Stable thermal radical curable silicone adhesive compositions

ABSTRACT

A stable thermal radical curable silicone composition is provided that comprises (I) a clustered functional polyorganopolysiloxane having one or more radical curable groups selected from an acrylate group and a methacrylate group; (II) a reactive resin and polymer; (III) a radical initiator; (IV) a moisture cure initiator; and (V) a crosslinker. The reactive resin and polymer includes (a) an organopolysiloxane polymer and (b) an alkoxy-functional organopolysiloxane resin. The alkoxy-functional organopolysiloxane resin comprises the reaction product of a reaction of (i) an alkenyl-functional siloxane resin, (ii) an alkoxysilane-functional organosiloxane, and (iii) an endcapper in the presence of (iv) hydrosilylation catalyst. The stable thermal radical curable silicone composition can be utilized for electronics applications.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a U.S. national stage filing under 35 U.S.C. §371 ofPCT Application No. PCT/US14/015571 filed on 10 Feb. 2014, currentlypending, which claims the benefit of U.S. Provisional Patent ApplicationNo. 61/763,123 filed 11 Feb. 2013 under 35 U.S.C. §119 (e). PCTApplication No. PCT/US14/015571 and U.S. Provisional Patent ApplicationNo. 61/763,123 are hereby incorporated by reference.

The present invention relates generally to stable thermal radicalcurable silicone adhesive compositions, and, more specifically, tostable thermal radical curable silicone adhesive composition comprising:(I) a clustered functional polyorganosiloxane having at least oneradical curable group selected from an acrylate group and a methacrylategroup, (II) a reactive resin and polymer, (III) a radical initiator,(IV) a moisture cure initiator; and (V) a crosslinker.

Polyorganosiloxane compositions that cure to elastomeric materials arewell known. Such compositions may be prepared by mixingpolydiorganosiloxanes having curable (e.g., hydrolyzable, radiationcurable, or heat curable) groups with crosslinking agents and/orcatalysts, as needed. Generally, the polydiorganosiloxanes may have 1 to3 reactive groups per chain end. Compositions including these componentscan then be cured, for example, by exposure to atmospheric moisture,exposure to radiation, or exposure to heat, depending on the curablegroups present.

The cure rate of a particular composition depends on various factorsincluding the type and number reactive group(s) present. It is knownthat different groups have different reactivities. For example, in thepresence of moisture, a silicon-bonded acetoxy group will usuallyhydrolyze more rapidly than a silicon-bonded alkoxy group when all otherconditions are the same. Furthermore, even the same type of curablegroup can have different reactivities depending on the number of thosecurable groups bonded to a particular silicon atom. For example, if apolydiorganosiloxane has three silicon-bonded alkoxy groups bonded toone silicon atom on a chain end, then the first alkoxy group isgenerally most reactive (reacts most quickly), but after the firstalkoxy group reacts, it takes a longer time for the second alkoxy groupbonded to the same silicon atom to react, and even longer for the third.Therefore, there is a continuing need to prepare clustered functionalpolyorganosiloxanes having more of the “most” reactive groups permolecular terminal.

Furthermore, to show utility for certain applications, such as siliconeadhesive applications, a filler may be added to the composition toimprove the physical property profile (e.g., increase tensile strengthand increase % elongation to break) of the resulting cured product ofthe composition. The nature of the filler, its chemistry, particle sizeand surface chemistry have all been shown to influence the magnitude ofthe interaction between polyorganosiloxanes and the filler andconsequently the ultimate physical properties. Other properties such asadhesion and dispensability also play a role in the performance andcommercial acceptance of a composition for adhesive applications.Silicone adhesives generally have tensile properties in excess of 200pounds per square inch (psi) and 100% elongation, with adhesion to awide variety of metal, mineral and plastic surfaces.

The synthesis of ‘dumb-bell’ silicone polymers, in which long polymerchains are capped with cyclic, linear and star-shaped species having oneor more organo-functional groups has been disclosed. Such polymers havebeen described which can undergo a number of cure chemistries, e.g.,epoxy (glycidyl, alkylepoxy, and cycloaliphatic epoxy), methacrylate,acrylate, urethanes, alkoxy, or addition.

It is desirable to make multifunctional end blocked polymers (clusteredfunctional polyorganosiloxanes) in which the curable groups areclustered at the ends/termini of the polymers. The combination ofclustered functional groups with nonfunctional polymer chains separatingthem in the ‘dumb-bell’ silicone polymers may provide higher physicalproperties with the minimum drop in cure rate. This approach has beendemonstrated for ‘dumb-bell’ silicone polymers in which the curablegroups are the same (for example, all curable groups clustered at thepolymer chain ends may be either epoxy or alkoxy). This approach hasalso been demonstrated for so called ‘multiple cure’ systems in whichthe curable groups differ, for example, all curable groups clustered atthe polymer terminals may be a combination of epoxy and alkoxy groups.

It is also desirable to make adhesive systems including these clusteredfunctional polyorganosiloxanes able to cure by more than one method ofcuring such that the adhesive products may be utilized on a wide varietyof substrates without losing any mechanical or physical properties.

BRIEF SUMMARY OF THE INVENTION

The present invention discloses a stable thermal radical curablesilicone adhesive composition comprising: (I) a clustered functionalpolyorganosiloxane having at least one radical curable group selectedfrom an acrylate group and a methacrylate group, (II) a reactive resinand polymer, (III) a radical initiator, (IV) a moisture cure initiator;and (V) a crosslinker.

In certain embodiments, the reactive resin and polymer (II) comprises:

(a) an organopolysiloxane polymer of the formula (R⁷O)_(3-z)R⁶_(z)Si-Q-(R²⁵ ₂SiO_(2/2))_(y)-Q-Sir⁶ _(z)(OR⁷)_(3-z),

wherein each R²⁵ is independently a monovalent hydrocarbon radicalhaving 1 to 6 carbon atoms, each R⁶ independently is a monovalenthydrocarbon radical having 1 to 6 carbon atoms, each R⁷ independently isselected from the group consisting of an alkyl radical and alkoxyalkylradical, Q is a divalent linking radical, the subscript z has a value of0, 1 or 2, and the subscript y has a value of 60 to 1000; and

(b) an alkoxy-functional organopolysiloxane resin comprising a reactionproduct of a reaction of:

(i) an alkenyl-functional siloxane resin comprising R²⁶ ₃SiO_(1/2) unitsand SiO_(4/2) units,

wherein each R²⁶ is independently a monovalent hydrocarbon radicalhaving 1 to 6 carbon atoms with the proviso that at least one R²⁶ is analkenyl radical,

wherein the molar ratio of the R²⁶ ₃SiO_(1/2) units to SiO_(4/2) unitshas a value of from 0.5/1 to 1.5/1,

(ii) an alkoxysilane-functional organosiloxane compound having at leastone silicon-bonded hydrogen atom at a molecular terminal;

(iii) an endcapper;

in the presence of a (iv) hydrosilylation catalyst.

The stable thermal radical curable silicone adhesive composition offersmany advantages over prior adhesive compositions due to its ability tocure by two distinct methods, namely moisture cure and thermal radicalcure, without adversely affecting its mechanical and physicalproperties. Thus, the stable thermal radical curable silicone adhesivecomposition may be used over a wider variety of substrates, includingplastic substrates and metal substrates, and in a wide variety ofapplication, such as in electronics applications. The reactive resin andpolymer (II) also aids in dispensing the adhesive composition by makingthe stable thermal radical curable silicone adhesive composition moreflowable, and thus it reduces stringing of the adhesive composition, forexample, as it is dispensed through a fine tip applicator.

DETAILED DESCRIPTION OF THE INVENTION

The articles ‘a’, ‘an’, and ‘the’ each refer to one or more, unlessotherwise indicated. All amounts, ratios, and percentages in thisapplication are by weight, unless otherwise indicated. All kinematicviscosities were measured at 25° C., unless otherwise indicated.

The present invention describes curable silicone compositions, such asan adhesive or a sealant, that are curable by a heat curing mechanismsuch as thermal radical initiation and a room temperature curingmechanism such as condensation reaction or organoborane initiation (whenan amine reactive compound is added instead of heat). The presentinvention may also use a radiation curing mechanism such as radiationradical initiation or redox reaction, or a combination thereof.

In certain embodiments, the curable silicone composition comprises (I) aclustered functional polyorganopolysiloxane; (II) a reactive resin andpolymer; (III) a radical initiator; (IV) a moisture cure initiator; and(V) a crosslinker.

Component (I) is a clustered functional polyorganopolysiloxane.

In certain embodiments the clustered functional polyorganopolysiloxane(I) may be formed as the reaction product of a reaction of:

a) a polyorganosiloxane having an average, per molecule, of at least 2aliphatically unsaturated organic groups;

b) a polyorganohydrogensiloxane having an average of 4 to 15 siliconatoms per molecule; and

c) a reactive species having, per molecule, at least 1 aliphaticallyunsaturated organic group and 1 or more curable groups;

in the presence of d) a hydrosilylation catalyst.

In certain embodiments, the weight percent of silicon bonded hydrogenatoms in the polyorganohydrogensiloxane b) divided by a weight percentof aliphatically unsaturated organic groups in the polyorganosiloxane a)(the SiH_(b)/Vi_(a) ratio) ranges from 4/1 to 20/1.

The clustered functional polyorganosiloxane produced in accordance withthe present invention may also include e) an isomer reducing agent,wherein the utilization of a sufficient amount of isomer reducing agente) results in a reduction, such as at least a 10% reduction, in theamount of D(Oz) units present in the formed clustered functionalpolyorganosiloxane, as measured by NMR, which corresponds to areduction, such as at least a 10% reduction, in the beta-addition of SiHgroups of the polyorganosiloxane (ii) to the aliphatically unsaturatedgroup of the reactive species c), as compared with clustered functionalpolyorganosiloxane formed in the absence of the isomer reducing agente).

In certain embodiments, a first embodiment of the process for formingthe clustered functional polyorganopolysiloxane (I) may comprise:

1) concurrently reacting components comprising

-   -   a) a polyorganosiloxane having an average, per molecule, of at        least 2 aliphatically unsaturated organic groups,    -   b) a polyorganohydrogensiloxane having an average, per molecule,        of 4 to 15 Si atoms and at least 4 silicon bonded hydrogen atoms        per aliphatically unsaturated organic group in component a), and    -   c) a reactive species having, per molecule, at least 1        aliphatically unsaturated organic group and 1 or more radical        curable groups selected from acrylate groups and methacrylate        groups;    -   in the presence of d) a hydrosilylation catalyst.

In this process, the components in step 1) may further comprise f) afiller, g) a non-reactive silicone resin, or a combination thereof. Theprocesses described above may optionally further comprise the steps of:2) adding a catalyst inhibitor to deactivate the catalyst after step 1),and 3) purifying the product of step 2).

Alternatively, a second embodiment of the process for forming theclustered functional polyorganopolysiloxane (I) may comprise:

I) concurrently reacting components comprising

-   -   a) the polyorganosiloxane having an average, per molecule, of at        least 2 aliphatically unsaturated organic groups; and    -   b) the polyorganohydrogensiloxane having an average, per        molecule, of 4 to 15 Si atoms and at least 4 silicon bonded        hydrogen atoms per aliphatically unsaturated organic group in        component a),    -   in the presence of d) the hydrosilylation catalyst; and        thereafter

II) reacting the product of step I) with an component comprising:

-   -   c) the reactive species having, per molecule, at least 1        aliphatically unsaturated organic group and one or more radical        curable groups selected from acrylate groups and methacrylate        groups;    -   with the proviso that the components in step I) and/or step II)        further comprise f) a filler, g) a non-reactive silicone resin,        or a combination thereof; and with the proviso that no        intermediate purification step is performed between step I) and        step II), and with the proviso that the SiH_(b)/Vi_(a) ratio        ranges from 4/1 to 20/1, and a product prepared by the process        has, on average, more than one curable group at each molecular        terminal of the polyorganosiloxane of component a).

The process may optionally further comprise the steps of: III) adding acatalyst inhibitor to deactivate the catalyst after step II), and IV)purifying the product of step III). The step of purifying the productsin the above processes may be performed by any convenient means, such asstripping or distillation, optionally under vacuum.

In certain embodiments, the clustered functional organopolysiloxane (I),in combination with the filler f) or (XII) as described below, comprisesfrom 50 to 95 weight percent, alternatively from 70 to 85 weightpercent, of the total weight of the silicone adhesive composition.

Component a) is a polyorganosiloxane having an average, per molecule, ofat least 2 aliphatically unsaturated organic groups, which are capableof undergoing a hydrosilylation reaction with a silicon bonded hydrogenatom of component b). Component a) may have a linear or branchedstructure. Alternatively, component a) may have a linear structure.Component a) may be a combination comprising two or morepolyorganosiloxanes that differ in at least one of the followingproperties: structure, viscosity, degree of polymerization, andsequence.

Component a) has a minimum average degree of polymerization (average DP)of 100. Alternatively, average DP of component a) may range from 100 to1000. The distribution DP of polyorganosiloxanes of component a) can bebimodal. For example, component a) may comprise one alkenyl terminatedpolydiorganosiloxane with a DP of 60 and another alkenyl terminatedpolydiorganosiloxane with a DP higher than 100, provided that average DPof the polydiorganosiloxanes ranges from 100 to 1000. However, suitablepolyorganosiloxanes for use in component a) have a minimum degree ofpolymerization (DP) of 10, provided that polyorganosiloxanes with DPless than 10 are combined with polyorganosiloxanes having DP greaterthan 100. Suitable polydiorganosiloxanes for component a) are known inthe art and are commercially available. For example, Dow Corning®SFD-128 has DP ranging from 800 to 1000, Dow Corning® SFD-120 has DPranging from 600 to 700, Dow Corning® 7038 has DP of 100, and DowCorning® SFD-119 has DP of 150. All of these are vinyl-terminatedpolydimethylsiloxanes are commercially available from Dow CorningCorporation of Midland, Mich., USA. When component a) has a bimodaldistribution, the polyorganosiloxane with the lower DP (low DPpolyorganosiloxane) is present in a lower amount than thepolyorganosiloxane with the higher DP (high DP polyorganosiloxane). Forexample, in a bimodal distribution, the ratio of low DPpolyorganosiloxane/high DP polyorganosiloxane may range from 10/90 to25/75.

Component a) may be exemplified by polyorganosiloxanes of formula (I),formula (II), or a combination thereof. Formula (I) is R¹ ₂R₂SiO(R¹₂SiO)_(a)(R¹R₂SiO)_(b)SiR¹ ₂R², and formula (II) is R¹ ₃SiO(R¹₂SiO)_(c)(R¹R²SiO)_(d)SiR¹ ₃. In these formulae, each R¹ isindependently a monovalent organic group free of aliphatic unsaturation,each R² is independently an aliphatically unsaturated organic group,subscript a has an average value ranging from 2 to 1000, subscript b hasan average value ranging from 0 to 1000, subscript c has an averagevalue ranging from 0 to 1000, and subscript d has an average valueranging from 4 to 1000. In formulae (I) and (II), 10≦(a+b)≦1000 and10≦(c+d)≦1000.

Suitable monovalent organic groups free of aliphatic unsaturation for R¹include, but are not limited to, monovalent hydrocarbon groupsexemplified by alkyl such as methyl, ethyl, propyl, butyl, pentyl,octyl, undecyl, and octadecyl; cycloalkyl such as cyclohexyl; and arylsuch as phenyl, tolyl, xylyl, benzyl, and 2-phenylethyl. R² may be analiphatically unsaturated monovalent hydrocarbon group exemplified byalkenyl groups such as vinyl, allyl, propenyl, and butenyl; and alkynylgroups such as ethynyl and propynyl.

Component a) may comprise a polydiorganosiloxane such as i)dimethylvinylsiloxy-terminated polydimethylsiloxane, ii)dimethylvinylsiloxy-terminatedpoly(dimethylsiloxane/methylvinylsiloxane), iii)dimethylvinylsiloxy-terminated polymethylvinylsiloxane, iv)trimethylsiloxy-terminated poly(dimethylsiloxane/methylvinylsiloxane),v) trimethylsiloxy-terminated polymethylvinylsiloxane, vi)dimethylvinylsiloxy-terminatedpoly(dimethylsiloxane/methylphenylsiloxane), vii)dimethylvinylsiloxy-terminated poly(dimethylsiloxane/diphenylsiloxane),viii) phenyl,methyl,vinyl-siloxy-terminated polydimethylsiloxane, ix)dimethylhexenylsiloxy-terminated polydimethylsiloxane, x)dimethylhexenylsiloxy-terminatedpoly(dimethylsiloxane/methylhexenylsiloxane), xi)dimethylhexenylsiloxy-terminated polymethylhexenylsiloxane, xii)trimethylsiloxy-terminated poly(dimethylsiloxane/methylhexenylsiloxane),or xiii) a combination thereof.

Component b) is a polyorganohydrogensiloxane having an average of 4 to15 silicon atoms per molecule. Component b) has an average of at least 4silicon bonded hydrogen atoms per aliphatically unsaturated organicgroup in component a). Component b) may be cyclic, branched, or linear.Alternatively, component b) may be cyclic. Component b) may be acombination comprising two or more polyorganohydrogensiloxanes thatdiffer in at least one of the following properties: structure,viscosity, degree of polymerization, and sequence.

Component b) may be a cyclic polyorganohydrogensiloxane having anaverage of 4 to 15 siloxanes per molecule. The cyclicpolyorganohydrogensiloxane may have formula (III), where formula (III)is (R³ ₂SiO_(2/2))_(e)(HR³SiO_(2/2))_(f), in which each R³ isindependently a monovalent organic group free of aliphatic unsaturation,subscript e has an average value ranging from 0 to 10, subscript f hasan average value ranging from 4 to 15, and a quantity (e+f) has a valueranging from 4 to 15, alternatively 4 to 12, alternatively 4 to 10,alternatively 4 to 6, and alternatively 5 to 6. Monovalent organicgroups suitable for R³ include, but are not limited to, monovalenthydrocarbon groups exemplified by alkyl such as methyl, ethyl, propyl,butyl, pentyl, octyl, undecyl, and octadecyl; cycloalkyl such ascyclohexyl; and aryl such as phenyl, tolyl, xylyl, benzyl, and2-phenylethyl.

Alternatively, component b) may be a branchedpolyorganohydrogensiloxane. The branched polyorganohydrogensiloxane forcomponent b) may have formula (IV), where formula (IV) is Si—(OSiR⁴₂)_(g)(OSiHR⁴)_(g), (OSiR⁴ ₃)_(h)(OSiR⁴ ₂H)_((4-h)), in which each R⁴ isindependently a monovalent organic group free of aliphatic unsaturation,subscript g has a value ranging from 0 to 10, subscript g′ has a valueranging from 0 to 10, and subscript h has a value ranging from 0 to 1.

Alternatively, subscript g may be 0. When subscript g′ is 0, thensubscript h is also 0. Monovalent organic groups suitable for R⁴include, but are not limited to, monovalent hydrocarbon groupsexemplified by alkyl such as methyl, ethyl, propyl, butyl, pentyl,octyl, undecyl, and octadecyl; cycloalkyl such as cyclohexyl; and arylsuch as phenyl, tolyl, xylyl, benzyl, and 2-phenylethyl.

Alternatively, component b) may be a linear polyorganohydrogensiloxanehaving an average of at least 4 silicon bonded hydrogen atoms permolecule. The linear polyorganohydrogensiloxane for component b) mayhave a formula selected from (V), (VI), or a combination thereof, whereformula (V) is R⁵ ₂HSiO(R⁵ ₂SiO)_(i)(R⁵HSiO)_(j)SiR⁵ ₂H, formula (VI) isR⁵ ₃SiO(R⁵ ₂SiO)_(k)(R⁵HSiO)_(m) SiR⁵ ₃; where each R⁵ is independentlya monovalent organic group free of aliphatic unsaturation, subscript ihas an average value ranging from 0 to 12, subscript j has an averagevalue ranging from 2 to 12, subscript k has an average value rangingfrom 0 to 12, and subscript m has an average value ranging from 4 to 12where 4≦(i+j)≦13 and 4≦(k+m)≦13. Monovalent organic groups suitable forR include, but are not limited to, monovalent hydrocarbon groupsexemplified by alkyl such as methyl, ethyl, propyl, butyl, pentyl,octyl, undecyl, and octadecyl; cycloalkyl such as cyclohexyl; and arylsuch as phenyl, tolyl, xylyl, benzyl, and 2-phenylethyl.

Component a) and component b) may be present in amounts sufficient toprovide a weight percent of silicon bonded hydrogen atoms in componentb) /weight percent of unsaturated organic groups in component a)(commonly referred to as SiH_(b)/Vi_(a) ratio) ranging from 4/1 to 20/1,alternatively 4/1 to 10/1, and alternatively 5/1 to 20/1. Withoutwishing to be bound by theory, it is thought that if SiH_(b)/Vi_(a)ratio is 30/1 or higher, the components may crosslink to form a productwith undesirable physical properties; and if SiH_(b)/Vi_(a) ratio isless than 4/1, the product of the process may not have sufficientclustered functional groups to have fast enough cure speed, particularlyif a monofunctional reactive species (having one curable group permolecule) is used as component c).

Without wishing to be bound by theory, it is thought that using anexcess of silicon bonded hydrogen atoms in component b), relative toaliphatically unsaturated organic groups in component a), may reduce thepossibilities of producing high homologs of the clustered functionalpolyorganosiloxanes, which tend to be insoluble in, and may reducestorage life of, a curable silicone composition containing the clusteredfunctional polyorganosiloxane prepared by the process described herein.The excess of silicon bonded hydrogen atoms in component b) may alsoresult in small (relatively low DP) clustered functionalpolyorganosiloxanes, which may act as reactive diluents or viscositymodifiers and adhesion promoters. It is difficult to make these highlyfunctional small molecules in an industrial environment because theinhibiting nature of small highly functional silicone hydrides meanstemperatures above 50° C. are typically required to initiate thehydrosilylation process. This is then followed by a large exotherm,which can be dangerous in the presence of large volumes of solvent, orif careful monitoring of reagents is not used to control thetemperature. By simply changing the SiH_(b)/Vi_(a) ratio, these speciescan be made in a dilute solution of clustered functionalpolyorganosiloxane and filler, thereby significantly reducing gelationand chance of fire due to uncontrolled exothermic reaction.

Component c) is a reactive species that may be any species that canprovide the curable groups in the clustered functionalpolyorganosiloxane (i.e., in the reaction product of a reaction ofcomponents a), b) and c)). The reactive species has an average, permolecule, of at least one aliphatically unsaturated organic group thatis capable of undergoing an addition reaction with a silicon bondedhydrogen atom of component b). Component c) further comprises one ormore radical curable groups per molecule. The radical curable groups arefunctional (reactive) groups that render the clustered functionalpolyorganosiloxane (prepared by the process described above) radiationcurable. The radical curable groups on component c) may be selected fromacrylate groups and methacrylate groups and combinations thereof.

For example, component c) may comprise a silane of formula (VIII), whereformula (VIII) is R⁸ _(o)SiR⁹ _((3-o)); in which subscript o has a valueranging from 1 to 3, each R⁸ is independently an aliphaticallyunsaturated organic group, and each R⁹ is independently selected from anorganic group containing an acrylate group and a methacrylate group.

Alternatively, component c) may comprise an organic compound (which doesnot contain a silicon atom). The organic compound for component c) mayhave an average, per molecule, of 1 to 2 aliphatically unsaturatedorganic groups, such as alkenyl or alkynyl groups, and one or morereactive groups selected from an acrylate group and a methacrylategroup. Examples of suitable organic compounds for component c) include,but are not limited to, allyl acrylate and allyl methacrylate (AMA) andcombinations thereof.

The amount of component c) depends on various factors including thetype, amount, and SiH content of component b) and the type of componentc) selected. However, the amount of component c) is sufficient to makeSiH_(tot)/Vi_(tot) range from 1/1 to 1/1.4, alternatively 1/1.2 to1.1/1. The ratio SiH_(tot)/Vi_(tot) means the weight percent of siliconbonded hydrogen atoms on component b) and, if present component g) thechain extender and/or component h) the endcapper (described below),divided by the weight percent of aliphatically unsaturated organicgroups on components a) and c) combined.

Component d) is a hydrosilylation catalyst which accelerates thereaction of components a), b), and c). Component d) may be added in anamount sufficient to promote the reaction of components a), b), and c),and this amount may be, for example, sufficient to provide 0.1 parts permillion (ppm) to 1000 ppm of platinum group metal, alternatively 1 ppmto 500 ppm, alternatively 2 ppm to 200, alternatively 5 ppm to 20 ppm,based on the combined weight of all components used in the process.

Suitable hydrosilylation catalysts are known in the art and commerciallyavailable. Component d) may comprise a platinum group metal selectedfrom platinum (Pt), rhodium, ruthenium, palladium, osmium or iridiummetal or organometallic compound thereof, or a combination thereof.Component d) is exemplified by compounds such as chloroplatinic acid,chloroplatinic acid hexahydrate, platinum dichloride, and complexes ofsaid compounds with low molecular weight organopolysiloxanes or platinumcompounds microencapsulated in a matrix or coreshell type structure.Complexes of platinum with low molecular weight organopolysiloxanesinclude 1,3-diethenyl-1,1,3,3-tetramethyldisiloxane complexes withplatinum. Alternatively, the catalyst may comprise1,3-diethenyl-1,1,3,3-tetramethyldisiloxane complex with platinum. Whenthe catalyst is a platinum complex with a low molecular weightorganopolysiloxane, the amount of catalyst may range from 0.04% to 0.4%based on the combined weight of the components used in the process.

Suitable hydrosilylation catalysts for component d) are described in,for example, U.S. Pat. Nos. 3,159,601; 3,220,972; 3,296,291; 3,419,593;3,516,946; 3,814,730; 3,989,668; 4,784,879; 5,036,117; and 5,175,325 andEP 0 347 895 B.

The components used in the process described above may optionallyfurther comprise one or more additional components selected from e) anisomer reducing agent, f) a filler, g) a non-reactive resin, h) a chainextender, and i) an endcapper, or a combination thereof. Alternatively,the components used in the process may be components a), b), c) d), e)and f). Alternatively, the components used in the process may becomponents a), b), c) d), e), f) and h). Alternatively, the componentsused in the process may be components a), b), c) d), e), f) and i).Alternatively, the components used in the process may be components a),b), c) d), e), f), h) and i).

Component e) is an isomer reducing agent. In certain embodiments, theisomer reducing agent comprises a carboxylic acid compound. Thecarboxylic acid compound may comprise (1) carboxylic acid, (2) ananhydride of a carboxylic acid, (3) a carboxylic silyl ester, and/or (4)a substance that will produce the above-mentioned carboxylic acidcompounds (i.e., (1), (2), and/or (3)) through a reaction ordecomposition in the reaction of the method. It is to be appreciatedthat a mixture of one or more of these carboxylic acid compounds may beutilized as the isomer reducing agent. For example, a carboxylic silylester may be utilized in combination with an anhydride of a carboxylicacid as the isomer reducing agent. In addition, a mixture within one ormore types of carboxylic acid compounds may be utilized as the isomerreducing agent. For example, two different carboxylic silyl esters maybe utilized in concert, or two carboxylic silyl esters may be utilizedin concert with an anhydride of a carboxylic acid.

When the isomer reducing agent e) comprises (1) carboxylic acid, anycarboxylic acid having carboxyl groups may be utilized. Suitableexamples of carboxylic acids include saturated carboxylic acids,unsaturated carboxylic acids, monocarboxylic acids, and dicarboxylicacids. A saturated or unsaturated aliphatic hydrocarbon group, aromatichydrocarbon group, halogenated hydrocarbon group, hydrogen atom, or thelike is usually selected as the portion other than the carboxyl groupsin these carboxylic acids. Specific examples of suitable carboxylicacids include saturated monocarboxylic acids such as formic acid, aceticacid, propionic acid, n-butyric acid, isobutyric acid, hexanoic acid,cyclohexanoic acid, lauric acid, and stearic acid; saturateddicarboxylic acids such as oxalic acid and adipic acid; aromaticcarboxylic acids such as benzoic acid and para-phthalic acid; carboxylicacids in which the hydrogen atoms of the hydrocarbon groups of thesecarboxylic acids have been substituted with a halogen atom or anorganosilyl group, such as chloroacetic acid, dichloroacetic acid,trifluoroacetic acid, para-chlorobenzoic acid, and trimethylsilylaceticacid; unsaturated fatty acids such as acrylic acid, methacrylic acid,and oleic acid; and compounds having hydroxy groups, carbonyl groups, oramino groups in addition to carboxyl groups, namely, hydroxy acids suchas lactic acid, keto acids such as acetoacetic acid, aldehyde acids suchas glyoxylic acid, and amino acids such as glutamic acid.

When the isomer reducing agent e) comprises (2) an anhydride ofcarboxylic acid, suitable examples of anhydrides of carboxylic acidsinclude acetic anhydride, propionic anhydride, and benzoic anhydride.These anhydrides of carboxylic acids may be obtained via a reaction ordecomposition in the reaction system include acetyl chloride, butyrylchloride, benzoyl chloride, and other carboxylic acid halides,carboxylic acid metal salts such as zinc acetate and thallium acetate,and carboxylic esters that are decomposed by light or heat, such as(2-nitrobenzyl) propionate.

In embodiments where the isomer reducing agent e) comprises (3) acarboxylic silyl ester, suitable examples of carboxylic silyl esters aretrialkylsilylated carboxylic acids, such as trimethylsilyl formate,trimethylsilyl acetate, triethylsilyl propionate, trimethylsilylbenzoate, and trimethylsilyl trifluoroacetate; and di-, tri-, ortetracarboxysilylates, such as dimethyldiacetoxysilane,diphenyldiacetoxysilane, methyltriacetoxysilane, ethyltriacetoxysilane,vinyltriacetoxysilane, di-t-butoxydiacetoxysilane, and silicontetrabenzoate.

The isomer reducing agent e) is typically utilized in an amount rangingfrom 0.001 to 1 weight percent, alternatively from 0.01 to 0.1 weightpercent, based on the total weight of the clustered functionalpolyorganopolysiloxane (I). Examples of commercially availablecarboxylic silyl esters suitable as the isomer reducing agent are DOWCORNING® ETS 900 or XIAMETER® OFS-1579 Silane, available from DowCorning Corporation of Midland, Mich. Another exemplary isomer reducingagent is 2,6,-Di-tert-butyl-4-(dimethylaminomethyl)phenol (DBAP).

The isomer reducing agent e), added in a sufficient amount ranging from0.001 to 1 weight percent as provided above, promotes the alpha-additionof the SiH groups of the polyorganosiloxane a) to the aliphaticallyunsaturated group of the reactive species c) over the beta-addition ofthe SiH groups of the polyorganosiloxane a) to the aliphaticallyunsaturated group of the reactive species c). The beta-position additionmay result in the subsequent further reaction of the polyorganosiloxanea) to generate Si—OH and associated silicon hydroxide product (sometimesreferred to as D(Oz) and/or T(Oz) units). Without being bound by anytheory, it is believed that the generation of Si—OH hastens moisturecure of the polyorganosiloxanes. The relative amount of D(Oz) unitsgenerated, which correlate to the amount of beta-position addition ofSiH groups of the polyorganosiloxane a) to the aliphatically unsaturatedgroup of the reactive species c), may be measured by NMR.

The clustered functional polyorganosiloxane (I) produced in accordancewith the present invention utilizing a sufficient amount of isomerreducing agent e) results in a reduction, and in certain embodiments atleast a 10% reduction, in the amount of D(Oz) units present in theformed clustered functional polyorganosiloxane, as measured by NMR,which corresponds to a reduction, and in certain embodiments at least a10% reduction, in the beta-addition of SiH groups of thepolyorganosiloxane a) to the aliphatically unsaturated group of thereactive species c).

Component f) is a filler that may be added during the process describedabove. Fillers are exemplified by reinforcing and/or extending fillerssuch as, alumina, calcium carbonate (e.g., fumed, ground, and/orprecipitated), diatomaceous earth, quartz, silica (e.g., fumed, ground,and/or precipitated), talc, zinc oxide, chopped fiber such as choppedKEVLAR®, or a combination thereof. The amount of filler will depend onvarious factors including the type of filler selected and the end use ofthe clustered functional polyorganosiloxane to be produced by theprocess. However, the amount of filler may be up to 20%, alternatively1% to 20%, based on the combined weight of all the components. When theclustered functional polyorganosiloxane prepared by the processdescribed above will be used in an adhesive composition, the amount offiller may range from 10% to 20%. Alternatively, when the clusteredfunctional polyorganosiloxane will be used in a sealant composition, theamount of filler may range from 4% to 10%.

Without wishing to be bound by theory, it is thought that when thefiller is added during the process described herein, this will providean improvement in tensile properties as compared to a prior art processin which a conventional ‘dumb-bell’ type polyorganosiloxane is formed ina multiple step process, and thereafter a filler is dispersed.Therefore, the process described herein in the first embodiment mayfurther comprise: mixing component f), a filler, with component a)before or during step 1) of the process described above. Alternatively,the process of the second embodiment may further comprise mixing f) afiller with component a) before or during step I) or mixing f) a fillerwith the components after step I) and before or during step II) of theprocess of the second embodiment described above.

The above process step of adding a filler may provide a benefit withmany curable groups, however, adverse reactions with clusteredfunctional polyorganosiloxanes (for example, containing hydrolyzablegroups) may still be problematic. To combat this problem, the process ofthe first embodiment may further comprise: mixing f) a filler and f) afiller treating agent with component a) before or during step 1) of theprocess described above. Alternatively, the process of the secondembodiment may further comprise mixing f) a filler and f′) a fillertreating agent with component a) before or during step I) or mixing f) afiller and f′) a filler treating agent with the components after step I)and before or during step II) of the process of the second embodimentdescribed above. The effective treatment of filler surfaces in situ asdescribed above may require elevated temperature and/or vacuumconditions. These conditions may also be undesirable with thermallysensitive unsaturated functional groups and their oxygen enabledantioxidants. Therefore, the filler may be pretreated with the fillertreating agent in the presence of component a) at elevated temperatureand/or under vacuum. These filler treating conditions may be performedin a batch or continuous process as described, for example, in U.S. Pat.No. 6,013,701 to Kunimatsu, et al.

The resulting combination of treated filler in polyorganosiloxane isreferred to as a masterbatch. Masterbatches are commercially available.The use of masterbatches allows the smooth reaction of the aliphaticallyunsaturated organic groups of component a) with the silicon bondedhydrogen atoms of component b) and unsaturated organic groups ofcomponent c) to be performed in a single, low shear step; leading tofilled clustered functional polyorganosiloxanes with superior tensileand adhesive properties along with improved rheological and storageproperties.

A masterbatch comprising a polyorganosiloxane having aliphaticallyunsaturated organic groups and a treated filler, with optionally asecond polyorganosiloxane (having aliphatically unsaturated organicgroups) of the same or differing molecular weight may be combined withcomponents b) and c), and the resulting mixture may be sheared beforeaddition of component d) at room temperature (RT). Reaction may then beinitiated by raising the temperature to 50° C. to 100° C., alternatively70° C. to 85° C., and maintaining the temperature until all of the SiHhas reacted, as measured by the time needed for the SiH peak as observedby Fourier Transform Infra Red spectroscopy (FT-IR) at about 2170 cm⁻¹,to be reduced into the background of the spectra.

Due to the thermal stability of the aliphatically unsaturatedpolyorganosiloxanes and filler treating agents, these processes can becarried out at higher temperatures and shear, yielding stable,reproducible masterbatches of treated filler (such as silica) inaliphatically unsaturated polyorganosiloxane (polymer) such as vinylendblocked PDMS. Not wanting to be constrained by theory, it is believedthat exposing the polymer/filler interface to high temperature andshear, optimizes polymer/filler interactions and produces stablemasterbatches. By using a masterbatch, one skilled in the art canformulate a curable silicone composition at low temperature and shear,which provides the benefit of making the process more widely applicableto prepare curable silicone compositions with different curechemistries.

The filler treating agent may be a treating agent, which is known in theart. The amount of filler treating agent may vary depending on variousfactors including the type and amounts of fillers selected for componentf) whether the filler is treated with filler treating agent in situ orpretreated before being combined with component a). However, thecomponents may comprise an amount ranging from 0.1% to 2% of fillertreating agent, based on the weight of the filler for component f).

The filler treating agent may comprise a silane such as an alkoxysilane,an alkoxy-functional oligosiloxane, a cyclic polyorganosiloxane, ahydroxyl-functional oligosiloxane such as a dimethyl siloxane or methylphenyl siloxane, a stearate, or a fatty acid. The alkoxysilane may havethe formula: R¹⁰ _(p)Si(OR¹¹)_((4-p)), where subscript p is 1, 2, or 3;alternatively p is 3. Each R¹⁰ is independently a monovalent organicgroup of 1 to 50 carbon atoms, such as a monovalent hydrocarbon group of1 to 50 carbon atoms, alternatively 6 to 18 carbon atoms. Suitablemonovalent hydrocarbon groups for R¹⁰ are exemplified by alkyl groupssuch as hexyl, octyl, dodecyl, tetradecyl, hexadecyl, and octadecyl; andaromatic groups such as benzyl, phenyl and phenylethyl. R¹⁰ can be amonovalent hydrocarbon group that is saturated or unsaturated andbranched or unbranched. Alternatively, R¹⁰ can be a saturated,unbranched, monovalent hydrocarbon group. Each R¹¹ may be a saturatedhydrocarbon group of 1 to 4 carbon atoms, alternatively 1 to 2 carbonatoms.

Alkoxysilane filler treating agents are exemplified byhexyltrimethoxysilane, octyltriethoxysilane, decyltrimethoxysilane,dodecyltrimethoxysilane, tetradecyltrimethoxysilane,phenyltrimethoxysilane, phenylethyltrimethoxysilane,octadecyltrimethoxysilane, octadecyltriethoxysilane, and a combinationthereof.

Alkoxy-functional oligosiloxanes can also be used as filler treatingagents. For example, suitable alkoxy-functional oligosiloxanes includethose of the formula (R¹⁴O)_(q)Si(OSiR¹² ₂R¹³)_((4-q)). In this formula,subscript q is 1, 2, or 3, alternatively q is 3. Each R¹² can beindependently selected from saturated and unsaturated monovalenthydrocarbon groups of 1 to 10 carbon atoms. Each R¹³ can be a saturatedor unsaturated monovalent hydrocarbon group having at least 10 carbonatoms. Each R¹⁴ can be an alkyl group.

Alternatively, alkoxysilanes may be used, but typically in combinationwith silazanes, which catalyze the less reactive alkoxysilane reactionwith surface hydroxyls. Such reactions are typically performed above100° C. with high shear with the removal of volatile by-products such asammonia, methanol and water.

Alternatively, the filler treating agent can be any of the organosiliconcompounds typically used to treat silica fillers. Examples oforganosilicon compounds include, but are not limited to,organochlorosilanes such as methyltrichlorosilane,dimethyldichlorosilane, and trimethyl monochlorosilane; organosiloxanessuch as hydroxy-endblocked dimethylsiloxane oligomer,hexamethyldisiloxane, and tetramethyldivinyldisiloxane; organosilazanessuch as hexamethyldisilazane and hexamethylcyclotrisilazane; andorganoalkoxysilanes such as methyltrimethoxysilane, C₆H₁₃Si(OCH₃)₃,C₈H₁₇Si(OC₂H₅)₃, C₁₀H₂₁Si(OCH₃)₃, C₁₂H₂₅Si(OCH₃)₃, C₁₄H₂₉Si(OC₂H₅)₃, andC₆H₅CH₂CH₂Si(OCH₃)₃, vinyltrimethoxysilane, vinyltriethoxysilane,3-glycidoxypropyltrimethoxysilane, and3-methacryloxypropyltrimethoxysilane.

Filler treating agents for thermally conductive fillers, such as aluminaor passivated aluminum nitride, may include alkoxysilyl functionalalkylmethyl polysiloxanes (e.g., partial hydrolysis condensate of R²⁷_(oo)R²⁸ _(pp)Si(OR²⁹)_((4-oo-pp)) or cohydrolysis condensates ormixtures), or similar materials where the hydrolyzable group maycomprise silazane, acyloxy or oximo. In all of these, a group tetheredto Si, such as R²⁷ in the formula above, is a long chain unsaturatedmonovalent hydrocarbon or monovalent aromatic-functional hydrocarbon.Each R²⁸ is independently a monovalent hydrocarbon group, and each R²⁹is independently a monovalent hydrocarbon group of 1 to 4 carbon atoms.In the formula above, subscript oo is 1, 2, or 3 and subscript pp is 0,1, or 2, with the proviso that a sum (oo+pp) is 1, 2, or 3.

Other filler treating agents include alkenyl functionalpolyorganosiloxanes. Suitable alkenyl functional polyorganosiloxanesinclude, but are not limited to:

where subscript q′ has a value up to 1,500. Other filler treating agentsinclude mono-endcapped alkoxy functional polydiorganosiloxanes, i.e.,polydiorganosiloxanes having an alkoxy group at one end. Such fillertreating agents are exemplified by the formula: R²⁵R²⁶ ₂SiO(R²⁶₂SiO)_(u), Si(OR²⁷)₃, where subscript u′ has a value of 0 to 100,alternatively 1 to 50, alternatively 1 to 10, and alternatively 3 to 6.Each R²⁵ is independently selected from an alkyl group, such as methyl,ethyl, propyl, butyl, hexyl, and octyl; and an alkenyl group, such asvinyl, allyl, butenyl, and Hex. Each R²⁶ is independently an alkyl groupsuch as methyl, ethyl, propyl, butyl, hexyl, and octyl. Each R²⁷ isindependently an alkyl group such as methyl, ethyl, propyl, and butyl.Alternatively, each R²⁵, each R²⁶, and each R²⁷ is methyl.Alternatively, each R²⁵ is vinyl. Alternatively, each R²⁶ and each R²⁷is methyl.

Alternatively, a polyorganosiloxane capable of hydrogen bonding isuseful as a treating agent. This strategy to treating surface of afiller takes advantage of multiple hydrogen bonds, either clustered ordispersed or both, as the means to tether the compatibilization moietyto the filler surface. The polyorganosiloxane capable of hydrogenbonding has an average, per molecule, of at least one silicon-bondedgroup capable of hydrogen bonding. The group may be selected from: anorganic group having multiple hydroxyl functionalities or an organicgroup having at least one amino functional group. The polyorganosiloxanecapable of hydrogen bonding means that hydrogen bonding is the primarymode of attachment for the polyorganosiloxane to a filler. Thepolyorganosiloxane may be incapable of forming covalent bonds with thefiller. The polyorganosiloxane capable of hydrogen bonding may beselected from the group consisting of a saccharide-siloxane polymer, anamino-functional polyorganosiloxane, and a combination thereof.Alternatively, the polyorganosiloxane capable of hydrogen bonding may bea saccharide-siloxane polymer.

The non-reactive silicone resin g) useful herein contains monofunctionalunits represented by R¹⁵ ₃SiO_(1/2) and tetrafunctional unitsrepresented by SiO_(4/2). R¹⁵ represents a nonfunctional monovalentorganic group such as a hydrocarbon group. The silicone resin is solublein liquid hydrocarbons such as benzene, toluene, xylene, heptane and thelike or in liquid organosilicon compounds such as a low viscosity cyclicand linear polydiorganosiloxanes.

In the R¹⁵ ₃SiO_(1/2) unit, R¹⁵ may be a monovalent hydrocarbon groupcontaining up to 20 carbon atoms, alternatively 1 to 10 carbon atoms.Examples of suitable monovalent hydrocarbon groups for R¹⁵ include alkylgroups, such as methyl, ethyl, propyl, butyl pentyl, octyl, undecyl andoctadecyl; cycloaliphatic radicals, such as cyclohexyl andcyclohexenylethyl; and aryl radicals such as phenyl, tolyl, xylyl,benzyl and 2-phenylethyl. Organic groups for R¹⁵ are exemplified by thehydrocarbon groups above modified such that where a non-reactivesubstituent has replaced a hydrogen atom, for example, the nonreactivesubstituents may include but are not limited to halogen and cyano.Typical organic groups that can be represented by R¹⁵ include but arenot limited to chloromethyl and 3,3,3-trifluoropropyl.

The molar ratio of the R¹⁵ ₃SiO_(1/2) and SiO_(4/2) units in thesilicone resin may range from 0.5/1 to 1.5/1, alternatively from 0.6/1to 0.9/1. These molar ratios are conveniently measured by Silicon 29Nuclear Magnetic Spectroscopy (²⁹Si NMR). This technique is capable ofquantitatively determining the concentration of R¹⁵ ₃SiO_(1/2) (“M”) andSiO_(4/2) (“Q”) units derived from the silicone resin, in addition tothe total hydroxyl content of the silicone resin.

The silicone resin may further comprise 2.0% or less, alternatively 0.7%or less, alternatively 0.3% or less, of terminal units represented bythe formula XSiO_(3/2), where X represents hydroxyl or a hydrolyzablegroup exemplified by alkoxy such as methoxy and ethoxy. Theconcentration of hydrolyzable groups present in the silicone resin canbe determined using FT-IR.

The weight average molecular weight, M_(w), will depend at least in parton the molecular weight of the silicone resin and the type(s) ofhydrocarbon groups, represented by R¹⁵, that are present in thiscomponent. M_(w) as used herein represents the molecular weight measuredusing gel permeation chromatography (GPC), when the peak representingthe neopentamer is excluded form the measurement. The M_(w) of thesilicone resin may range from 12,000 to 30,000 g/mole, typically 17,000to 22,000 g/mole.

The silicone resin can be prepared by any suitable method. Siliconeresins of this type have been prepared by cohydrolysis of thecorresponding silanes or by silica hydrosol capping methods known in theart. The silicone resin may be prepared by the silica hydrosol cappingprocesses of Daudt, et al., U.S. Pat. No. 2,676,182; of Rivers-Farrellet al., U.S. Pat. No. 4,611,042; and of Butler, U.S. Pat. No. 4,774,310.

The intermediates used to prepare the silicone resin are typicallytriorganosilanes of the formula R¹⁵ ₃SiX′, where X′ represents ahydrolyzable group, and either a silane with four hydrolyzable groupssuch as halogen, alkoxy or hydroxyl, or an alkali metal silicate such assodium silicate.

It is desirable that the silicon-bonded hydroxyl groups (i.e.,HOR¹⁵SiO_(1/2) or HOSiO_(3/2) groups) in the silicone resin be below1.0% based on the total weight of the silicone resin, alternativelybelow 0.3%. Silicon-bonded hydroxyl groups formed during preparation ofthe silicone resin may be converted to trihydrocarbylsiloxy groups or ahydrolyzable group by reacting the silicone resin with a silane,disiloxane or disilazane containing the appropriate terminal group.Silanes containing hydrolyzable groups are typically added in excess ofthe quantity required to react with the silicon-bonded hydroxyl groupsof the silicone resin.

Component h) is a chain extender. The chain extender may be apolydiorganosiloxane terminated at both ends with hydrogen atoms. Anexemplary chain extender may have the formula (XVII): HR¹⁶ ₂Si—(R¹⁶₂SiO)_(r)—SiR¹⁶ ₂H, where each R¹⁶ is independently a monovalenthydrocarbon group exemplified by alkyl such as methyl, ethyl, propyl,butyl, pentyl, and hexyl; and aryl such as phenyl, tolyl, xylyl, andbenzyl. Subscript r has an average value ranging from 0 to 400,alternatively 10 to 100.

Whether to use a chain extender, and the amount used when present,depends on various factors including the degree of crosslinking inherentin the system. For example, when starting with a polyorganosiloxane forcomponent a) which has a relatively low average DP, e.g., average DPranging from 60 to 400, then 50 mole % to 80 mole % of the SiH contentin all of the components combined may come from the chain extender,alternatively 70 mole %. When using longer vinyl endblocked polymer(average DP>400) then lower levels are effective, e.g., 25 mole % to 50mole % of SiH from chain extending molecules, preferably 40 mole %.

Component i) is an endcapper. The endcapper may be apolydiorganosiloxane having one silicon-bonded hydrogen atom permolecule. An exemplary endcapper may have the formula (XVIII), formula(XIX), or a combination thereof. Formula (XVIII) is R¹⁷ ₃SiO—(R¹⁷₂SiO)_(s)—SiR¹⁷ ₂H. Each R¹⁷ is independently a monovalent hydrocarbongroup exemplified by alkyl such as methyl, ethyl, propyl, butyl, pentyl,and hexyl; and aryl such as phenyl, tolyl, xylyl and benzyl; andsubscript s has a value ranging from 0 to 10, alternatively 1 to 10, andalternatively 1. Formula (XIX) is R¹⁸ ₃SiO—(R¹⁸₂SiO)_(t)—(HR¹⁸SiO)—SiR¹⁸ ₃. In this formula, each R¹⁸ is independentlya monovalent hydrocarbon group exemplified by alkyl such as methyl,ethyl, propyl, butyl, pentyl, and hexyl; and aryl such as phenyl, tolyl,xylyl and benzyl. Subscript t has a value ranging from 0 to 10,alternatively 0.

Alternatively, one of a chain extender or an endcapper is used; i.e., inthis instance, the chain extender and the endcapper are not incombination with each other.

The endcapper may provide the benefit of producing a looser network ofhigher tensile properties when used as a mole percentage of theavailable SiH in the system. The amount of endcapper added may rangefrom 0 to 15%, alternatively 2% to 15%, and alternatively 10%, based onthe combined weight of all components used in the process.

A secondary benefit of having a chain extender or an endcapper in theprocess is initial reduction in viscosity prior to reaction, which mayfacilitate the reaction and reduce the tendency for gelation due toinsufficient mixing and local gel formation. Using a chain extender oran endcapper may be especially beneficial when using relatively highmolecular weight polyorganosiloxanes for component a) (e.g., average DPgreater than 400) and when a filler is present.

The weight percent of silicon bonded hydrogen atoms in thecomponents/weight percent of unsaturated organic groups capable ofundergoing hydrosilylation in the components (commonly referred to asSiH_(tot)/Vi_(tot) ratio) may range from 1/1.4 to 1/1, alternatively1/1.2 to 1/1.1. In this ratio, SiH_(tot) refers to the amount of siliconbonded hydrogen atoms in component b) in combination with the amount ofsilicon bonded hydrogen atoms in components h) and/or i), if present.Vi_(tot) refers to the total amount of aliphatically unsaturated organicgroups in components a) and c) combined.

Component j) is a catalyst inhibitor. Component j) may optionally beadded after step 1) in the method of the first embodiment describedabove or after step II) in the method of the second embodiment describedabove to stop the reaction and stabilize the clustered functionalpolyorganosiloxane prepared by the process described above. Someexamples of suitable catalyst inhibitors include ethylenically oraromatically unsaturated amides, acetylenic compounds such as2-ethynyl-isopropanol, 2-ethynyl-butane-2-ol, 2-methyl-3-butyn-2-ol,2-phenyl-3-butyn-2-ol, 3,5-dimethyl-1-hexyn-3-ol,1-ethynyl-1-cyclohexanol, 1,5-hexadiene, 1,6-heptadiene;3,5-dimethyl-1-hexen-1-yne; 3-ethyl-3-buten-1-yne or3-phenyl-3-buten-1-yne; ethylenically unsaturated isocyanates; silylatedacetylenic alcohols exemplified by trimethyl(3,5-dimethyl-1-hexyn-3-oxy)silane,dimethyl-bis-(3-methyl-1-butyn-oxy)silane,methylvinylbis(3-methyl-1-butyn-3-oxy)silane, and((1,1-dimethyl-2-propynyl)oxy)trimethylsilane; unsaturated hydrocarbondiesters; conjugated ene-ynes exemplified by 2-isobutyl-1-butene-3-yne,3,5-dimethyl-3-hexene-1-yne, 3-methyl-3-pentene-1-yne,3-methyl-3-hexene-1-yne, 1-ethynylcyclohexene, 3-ethyl-3-butene-1-yne,and 3-phenyl-3-butene-1-yne; olefinic siloxanes such as1,3-divinyltetramethyldisiloxane, 1,3,5,7-tetravinyltetramethylcyclotetrasiloxane, or 1,3-divinyl-1,3-diphenyldimethyldisiloxane;1,3,5,7-tetramethyl-1,3,5,7-tetravinylcyclotetrasiloxane; a mixture of aconjugated ene-yne as described above and an olefinic siloxane asdescribed above; hydroperoxides; nitriles and diaziridines; unsaturatedcarboxylic esters exemplified by diallyl maleate, dimethyl maleate,diethyl fumarate, diallyl fumarate, andbis-2-methoxy-1-methylethylmaleate, mono-octylmaleate,mono-isooctylmaleate, mono-allyl maleate, mono-methyl maleate,mono-ethyl fumarate, mono-allyl fumarate, and2-methoxy-1-methylethylmaleate; fumarates such as diethylfumarate;fumarate/alcohol mixtures wherein the alcohol is benzyl alcohol or1-octanol and ethenyl cyclohexyl-1-ol; a nitrogen-containing compoundsuch as tributylamine, tetramethylethylenediamine, benzotriazole; asimilar phosphorus-containing compound such as triphenylphosphine; asulphur-containing compound; a hydroperoxy compound; or a combinationthereof.

The inhibitors are used in an amount effective to deactivate componentd) the hydrosilylation catalyst. The amount will vary depending on thetype and amount of catalyst and the type of inhibitor selected, however,the amount may range from 0.001 to 3 parts by weight, and alternativelyfrom 0.01 to 1 part by weight per 100 parts by weight of component a).

Component (II) is reactive resin and polymer. The reactive resin andpolymer (II) aids in dispensing the adhesive composition by make theadhesive composition more flowable, and thus it reduces stringing of theadhesive composition, for example, as it is dispensed through a fine tipapplicator.

In certain embodiments, the reactive resin and polymer (II) comprises:

(a) an organopolysiloxane polymer of the formula (OR)_(3-z)R⁶_(z)Si-Q-(R²⁵ ₂SiO_(2/2))_(y)-Q-SiR⁶ _(z)(OR⁷)_(3-z),

wherein each R²⁵ is independently a monovalent hydrocarbon radicalhaving 1 to 6 carbon atoms, each R⁶ independently is a monovalenthydrocarbon radical having 1 to 6 carbon atoms, each R⁷ independently isselected from the group consisting of an alkyl radical and alkoxyalkylradical, Q is a divalent linking radical, the subscript z has a value of0, 1 or 2, and the subscript y has a value of 60 to 1000; and

(b) an alkoxy-functional organopolysiloxane resin comprising thereaction product of:

(i) an alkenyl-functional siloxane resin comprising R²⁶ ₃SiO_(1/2) unitsand SiO_(4/2) units,

wherein each R²⁶ is independently a monovalent hydrocarbon radical have1 to 6 carbon atoms with the proviso that at least one R²⁶ is an alkenylradical,

wherein the molar ratio of the R²⁶ ₃SiO_(1/2) units to SiO_(4/2) unitshas a value of from 0.5/1 to 1.5/1,

(ii) an alkoxysilane-functional organosiloxane compound having at leastone silicon-bonded hydrogen atom at a molecular terminal;

(iii) an endcapper;

in the presence of a (iv) hydrosilylation catalyst.

In certain embodiments, the weight ratio of the polymer (a) to resin (b)in the reactive resin and polymer (II) varies from 75/25 to 35/65.

The organopolysiloxane polymer (a), as noted above, comprises theformula (R⁷O)_(3-z)R⁶ _(z)Si-Q-(R²⁵ ₂SiO_(2/2))_(y)-Q-SiR⁶_(z)(OR⁷)_(3-z), wherein each R is independently a monovalenthydrocarbon radical having 1 to 6 carbon atoms, each R⁶ independently isa monovalent hydrocarbon radical having 1 to 6 carbon atoms, each R⁷independently is selected from the group consisting of an alkyl radicaland alkoxyalkyl radical, Q is a divalent linking radical, the subscriptz has a value of 0, 1 or 2, and the subscript y has a value of 60 to1000.

The Q radical is a divalent linking radical linking the silicon atom ofthe curing radical to a silicon atom of the resin. Q is typicallyselected from the types of divalent radicals that are used to linksilicon atoms in a hydrolytically stable manner and include, but are notlimited to, hydrocarbons such as alkylene, for example ethylene,propylene, and isobutylene and phenylene; siloxanes such as, forexample, polydimethylsiloxane; and combinations thereof. Preferably, thenumber of carbon atoms in the Q divalent linking radical numbers from 2to 12, alternatively 2, and the number of siloxane repeat units in the Qdivalent linking radical numbers from 0 to 20, alternatively 2.

As noted above, the alkoxy-functional organopolysiloxane resin (b)includes an alkenyl-functional siloxane compound (i) which, in certainembodiments, includes a resinous portion wherein the R²⁶ ₃SiO_(1/2)units (i.e., M units) are bonded to the SiO_(4/2) units (i.e., Q units),each of which is bonded to at least one other SiO_(4/2) unit. In the R²⁶₃SiO_(1/2) units, each R²⁶ is individually a monovalent hydrocarbonradical having less than 6 carbon atoms, with the proviso that at leastone R²⁶ is an alkenyl radical. Examples of suitable R²⁶ radicals includealkyl radicals, such as methyl, ethyl, propyl, and pentyl; alkenylradicals, such as vinyl, alkyl, and 5-hexenyl; and aryl radicals such asphenyl.

At least one third, and more preferably substantially all R²⁶ radicals,are methyl radicals, with the proviso that at least one R radical is analkenyl radical, and further with the proviso that the resin (i)includes from 0.5 to 4 weight percent, alternatively from 1.0 to 2.2weight percent, alkenyl-functionality, based on the total weight of theresin (i). Stated differently, the alkenyl radical content of the resin(i) is from 0.05 to 4 weight percent of the total weight of the resin(i). Examples of preferred R²⁶ ₃SiO_(1/2) units having methyl radicalsinclude Me₃SiO_(1/2) units and PhMe₂SiO_(1/2) units, wherein Me ismethyl and Ph is phenyl.

In addition, it is preferable that the hydroxyl content of the resin (i)is less than 1 weight percent of the total weight of the resin (i).

For the purposes of the present invention, the ratio of R²⁶ ₃SiO_(1/2)units to SiO_(4/2) units in resin (i) has a molar ratio of 0.5:1 to1.5:1, respectively. It is preferred that the molar ratio of the total Munits to total Q units of the resin (i) be between 0.6:1 and 1.0:1. Theabove M/Q molar ratios can be easily obtained by ²⁹Si nuclear magneticresonance (NMR) spectroscopy.

The resin (i) preferably has a weight average molecular weight Mw from12,000 to 30,000 g/mole, typically between 17,000 and 22,000 g/mole.

As noted above, the alkoxy-functional organopolysiloxane resin (b) alsoincludes an alkoxysilane-functional organosiloxane compound having atleast one silicon-bonded hydrogen atom at a molecular terminal (ii)which, in certain embodiments, is of the general formulaHSi(R²⁷)₂OSi(R²⁷)₂CH₂CH₂SiR²⁷ _(zz)(OR)_(3-zz) wherein each R₂₇ isindependently a monovalent hydrocarbon having 1 to 6 carbon atoms andwherein the subscript zz is 0 or 1.

Even more preferably, the alkoxysilane-functional organosiloxanecompound having at least one silicon-bonded hydrogen atom at a molecularterminal (ii) is of the general formula HSi(Me)₂OSi(Me)₂CH₂CH₂Si (OMe)₃,wherein Me is methyl.

As noted above, the alkoxy-functional organopolysiloxane resin (b) alsoincludes an endcapper (iii). The endcapper (iii) is the same endcapperdescribed previously as component i) in the clustered functionalpolyorganosiloxane (I) above and preferably is of the formula (XVIII),formula (XIX), or a combination thereof.

As noted above, the alkoxy-functional organopolysiloxane resin andpolymer includes a hydrosilylation catalyst (iv) which accelerates thereaction of components (i)-(iii). Component (iv) may be added in anamount sufficient to promote the reaction of components (i)-(iii), andthis amount may be, for example, sufficient to provide 0.1 parts permillion (ppm) to 1000 ppm of platinum group metal, alternatively 1 ppmto 500 ppm, alternatively 2 ppm to 200, alternatively 5 ppm to 150 ppm,based on the combined weight of all components used in the process.

Suitable hydrosilylation catalysts are known in the art and commerciallyavailable. Component (iv) may comprise a platinum group metal selectedfrom platinum (Pt), rhodium, ruthenium, palladium, osmium or iridiummetal or organometallic compound thereof, or a combination thereof.Component (iv) is exemplified by compounds such as chloroplatinic acid,chloroplatinic acid hexahydrate, platinum dichloride, and complexes ofsaid compounds with low molecular weight organopolysiloxanes or platinumcompounds microencapsulated in a matrix or coreshell type structure.Complexes of platinum with low molecular weight organopolysiloxanesinclude 1,3-diethenyl-1,1,3,3-tetramethyldisiloxane complexes withplatinum. Alternatively, the catalyst may comprise1,3-diethenyl-1,1,3,3-tetramethyldisiloxane complex with platinum. Whenthe catalyst is a platinum complex with a low molecular weightorganopolysiloxane, the amount of catalyst may range from 0.04% to 0.4%based on the combined weight of the components used in the process.

Suitable hydrosilylation catalysts for component (iv) are described in,for example, U.S. Pat. Nos. 3,159,601; 3,220,972; 3,296,291; 3,419,593;3,516,946; 3,814,730; 3,989,668; 4,784,879; 5,036,117; and 5,175,325 andEP 0 347 895 B.

In certain other embodiments, the reactive resin and polymer (II) rangesfrom 5 to 50 weight percent, alternatively from 15 to 35 weight percent,of the total weight of the silicone adhesive composition.

Component (III) is a radical initiator. The radical initiator may be athermal radical initiator. Thermal radical initiators include, but arenot limited to, dicumyl peroxide, n-butyl 4,4′-bis(butylperoxy)valerate,1,1-bis(t-butylperoxy)-3,3,5 trimethyl cyclohexane, di-t-butyl peroxideand 2,5-di-(t-butylperoxy)-2,5 dimethyl hexane,1,1-bis(tert-amylperoxy)cyclohexane (Luperox® 531M80);2,2-bis(tert-butylperoxy)butane; 2,4-pentanedione peroxide (Luperox®224), 2,5-bis(tert-butylperoxy)-2,5-dimethylhexane (Luperox® 101),2,5-di(tert-butylperoxy)-2,5-dimethyl-3-hexyne; 2-butanone peroxide,benzoyl peroxide, cumene hydroperoxide, di-tert-amyl peroxide (Luperox®DTA®), lauroyl peroxide (Luperox® LP), tert-butyl hydroperoxide;tert-butyl peracetate; tert-butyl peroxybenzoate; tert-butylperoxy2-ethylhexyl carbonate; di(2,4-dichlorobenzoyl) peroxide;dichlorobenzoylperoxide (available as Varox® DCBP from R. T. VanderbiltCompany, Inc. of Norwalk, Conn., USA);di(tert-butylperoxyisopropyl)benzene, di(4-methylbenzoyl) peroxide,butyl 4,4-di(tert-butylperoxy)valerate,3,3,5,7,7-pentamethyl-1,2,4-trioxepane; tert-butylperoxy-3,5,5-trimethylhexanoate; tert-butyl cumyl peroxide;di(4-tert-butylcyclohexyl) peroxydicarbonate (available as Perkadox 16);dicetyl peroxydicarbonate; dimyristyl peroxydicarbonate;2,3-dimethyl-2,3-diphenylbutane, dioctanoyl peroxide; tert-butylperoxy2-ethylhexyl carbonate; tert-amyl peroxy-2-ethylhexanoate, tert-amylperoxypivalate; and combinations thereof.

Examples of such thermal radical initiators are commercially availableunder the following trade names: Luperox® sold by Arkema, Inc. ofPhiladelphia, Pa., U.S.A.; Trigonox and Perkadox sold by Akzo NobelPolymer Chemicals LLC of Chicago, Ill., U.S.A., VAZO sold by E.I. duPontdeNemours and Co. of Wilmington, Del., U.S.A; VAROX® sold by R.T.Vanderbilt Company, Inc. of Norwalk, Conn., U.S.A.; and Norox sold bySyrgis Performance Initiators, Inc. of Helena, Ark., U.S.A.

Alternatively, the curing agent may comprise a room temperature radicalinitiator such as an organoborane-amine complex. The organoborane aminecomplex is a complex formed between an organoborane and a suitable aminecompound that renders the complex stable at ambient conditions. Thecomplex should be capable of initiating polymerization or crosslinkingof component (I) by the introduction of an amine reactive compoundand/or by heating. An example is an alkylborane amine complex formedfrom trialkylboranes and various amine compounds. While the preferredmolar ratio can vary, the optimal molar ratio may range from 1 to 10nitrogen groups per B atom where B represents boron. Examples oftrialkylboranes useful for forming the curing agent includetrialkylboranes of the formula B—R″₃ where R″ represents linear andbranched aliphatic or aromatic hydrocarbon groups containing 1 to 20carbon atoms. Some examples include trimethylborane, tri-n-butylborane,tri-n-octylborane, tri-sec-butylborane, tridodecylborane, andphenyldiethylborane.

Some examples of amine compounds useful to form the organoborane aminecomplex with the organoborane compounds include 1,3 propane diamine,1,6-hexanediamine, methoxypropylamine, pyridine, and isophorone diamine.Other examples of amine compounds useful to form organoborane aminecomplexes are described in U.S. Pat. No. 6,777,512 (the '512 patent), aswell as in U.S. Pat. No. 6,806,330.

Silicon containing amine compounds can also be used to form theorganoborane amine complex including compositions such as3-aminopropyltrimethoxysilane, aminomethyltrimethoxysilane,3-aminopropyltriethoxysilane, aminomethyltriethoxysilane,2-(trimethoxysilylethyl)pyridine, aminopropylsilanetriol,3-(m-aminophenoxy)propyltrimethoxysilane,3-aminopropyldiisopropylmethoxysilane, aminophenyltrimethoxysilane,3-aminopropyltris(methoxyethoxethoxy)silane,N-(2-aminoethyl)-3-aminopropyltrimethoxysilane,N-(2-aminoethyl)aminomethyltrimethoxysilane,N-(6-aminohexyl)aminomethyltrimethoxysilane,N-(2-aminoethyl)-11-aminoundecyltrimethoxysilane,(aminoethylaminomethyl)phenethyltrimethoxysilane,N-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane,N-(2-aminoethyl)-3-aminoisobutylmethyldimethoxysilane, and(3-trimethoxysilylpropyl)diethylene-triamine.

Amine functional polyorganosiloxanes are also useful for forming theorganoborane amine complex including amine functionalpolydiorganosiloxanes, and amine functional polyorganosiloxane resins.This is subject to the stipulation that the molecule contain at leastone amine-functional group, such as 3-aminopropyl, 2-aminoethyl,aminomethyl, 6-aminohexyl, 11-aminoundecyl, 3-(N-allylamino)propyl,N-(2-aminoethyl)-3-aminopropyl, N-(2-aminoethyl)-3-aminoisobutyl,p-aminophenyl, 2-ethylpyridine, and 3-propylpyrrole.

Specific examples include terminal and/or pendant amine-functionalpolydimethylsiloxane oligomers and polymers, terminal and/or pendantamine-functional random, graft and block copolymers and co-oligomers ofpolydimethylsiloxane and poly(3,3,3 trifluoropropyl-methylsiloxane),terminal and/or pendant amine-functional random, graft and blockcopolymers and co-oligomers of polydimethylsiloxane andpoly(6,6,6,5,5,4,4,3,3-nonfluorohexyl-methylsiloxane), and terminaland/or pendant amine-functional random, graft and block copolymers andco-oligomers of polydimethylsiloxane and polyphenylmethylsiloxane.

Also useful to form the organoborane amine complex are other nitrogencontaining compounds includingN-(3-triethyoxysilylpropyl)-4,5-dihydroimidazole,ureidopropyltriethoxysilane, nitrogen containing polyorganosiloxanes,and polyorganosiloxane resins in which at least one group is animidazole, amidine, or ureido functional group. When the amine compoundis polymeric, the molecular weight is not limited, except that it shouldbe such as to maintain a sufficiently high concentration of boron topermit curing or polymerization of the composition. For example, in atwo-part composition, the part containing the organoborane initiator maybe diluted with other components of the composition, or it may consistof the initiator complex alone.

When an organoborane amine complex is used as the curing agent, thecurable silicone composition may further comprise an amine reactivecompound that is capable of initiating the polymerization orcrosslinking of the composition when mixed with the organoborane aminecomplex and exposed to an oxygenated environment. The presence of theamine reactive compound allows the initiation of polymerization orcrosslinking to occur at temperatures below the dissociation temperatureof the organoborane amine complex including room temperature and below.To achieve storage stability in the presence of oxygen, the organoboraneamine complex and the amine reactive compound may be physically orchemically isolated. For example, a composition containing an aminereactive compound can be rendered air stable by packaging it separatelyfrom the organoborane amine complex as a multiple-part composition.Alternatively, the organoborane amine complex, the amine reactivecompound, or both can be encapsulated, or delivered in separate phases.This can be accomplished by introducing one or both of the organoboraneamine complex, the amine reactive compound in a solid form that preventsintimate mixing of the organoborane amine complex, the amine reactivecompound. Curing of the composition can be activated by (a) heating itabove the softening temperature of the solid phase component orencapsulant, or (b) by introduction of a solubilizing agent that allowsmixing of the organoborane amine complex, the amine reactive compound.The organoborane amine complex, the amine reactive compound can also becombined in a single container without significant polymerization orcrosslinking by packaging the two components in a container where mixingconditions are anaerobic.

Examples of some amine reactive compounds having amine reactive groupsthat can rapidly initiate polymerization or cure in the presence ofoxygen include mineral acids, Lewis acids, carboxylic acids, carboxylicacid derivatives such as anhydrides and succinates, carboxylic acidmetal salts, isocyanates, aldehydes, epoxides, acid chlorides, andsulphonyl chlorides. Some suitable amine reactive compounds includeacrylic acid, polyacrylic acid, methacrylic acid, polymethacrylic acid,methacrylic anhydride, polymethacrylic anhydride, undecylenic acid,oleic acid, isophorone diisocyanate, methacryloylisocyanate,2-(methacryloyloxy)ethyl acetoacetate, undecylenic aldehyde, and dodecylsuccinic anhydride.

For improved compatibility in curable silicone compositions the aminereactive compound may be an organosilane or organopolysiloxane bearingamine reactive groups. Some examples include3-isocyanatopropyltrimethoxysilane; isocyanatomethyltrimethoxysilane;3-glycidoxypropyltrimethoxysilane; triethoxysilylpropyl succinicanhydride; propylsuccinic anhydride functionalized linear, branched,resinous, and hyperbranched organopolysiloxanes; methylsuccinicanhydride functionalized linear, branched, resinous, and hyperbranchedorganopolysiloxanes; cyclohexenyl anhydride functional linear, resinous,and hyperbranched organopolysiloxanes; carboxylic acid functionalizedlinear, branched, resinous, and hyperbranched organopolysiloxanes suchas carboxydecyl terminated oligomeric or polymericpolydimethylsiloxanes; and aldehyde functionalized linear, branched,resinous, and hyperbranched organopolysiloxanes such as undecylenicaldehyde-terminated oligomeric or polymeric polydimethylsiloxanes. The'512 patent describes silicon containing compounds that can be usedincluding certain compounds that release an acid when exposed tomoisture. The '512 patent also describes other amine reactive compoundsreferred to as decomplexation agents. Alternatively, the decomplexationagent may be selected from acids, anhydrides, isocaynates, or epoxies.Specific examples include 3-(triethoxysilyl)propylsuccinicanhydride,nonenyl succinic anhydride, acetic acid, 2-carboxyethylacrylate,ethylene glycol methacrylate phosphate, and acrylic acid.

Alternatively, the room temperature radical initiator comprises a redoxreagent as an initiator for radical polymerization. The reagent may be acombination of a peroxide and an amine or a transition metal chelate.The redox reagent is exemplified by, but not limited to, diacylperoxides such as benzoyl peroxide and acetyl peroxide; hydroperoxidessuch as cumene hydroperoxide and t-butyl hydroperoxide; ketone peroxidessuch as methyl ethyl ketone peroxide and cyclohexanone peroxide; dialkylperoxides such as dicumyl peroxide and ti-t-butyl peroxide; peroxyesters such as t-butyl peroxy acetate; and combinations of thioglyceroland pyrazoles and/or pyrazolones. Alternatively, the redox reagent maybe exemplified by dimethylaniline, 3,5-dimethylpyrazole, thioglycerol;and combinations thereof. Examples of suitable redox reagent initiatorsare known in the art and are exemplified as in U.S. Pat. No. 5,459,206.Other suitable peroxides are known in the art and are commerciallyavailable such as lauroyl peroxide (Luperox® LP from Arkema),dichlorobenzoylperoxide (Varox® DCBP from R. T. Vanderbilt Company,Inc.) and 6N tert-butyl hydroperoxide.

The concentration of the radical initiator (III) may range from 0.01% to15%, alternatively from 0.1% to 5%, and alternatively 0.1% to 2%, basedon the weight of the clustered functional polyorganosiloxane (I).

Component (IV) is a moisture cure initiator (i.e., a condensationcatalyst or condensation reaction catalyst). Examples of condensationreaction catalysts are known in the art and are disclosed in U.S. Pat.Nos. 4,962,076; 5,051,455; 5,053,442; 4,753,977 at col. 4, line 35 tocol. 5, line 57; and 4,143,088 at col. 7, line 15 to col. 10, line 35.The amount of the condensation reaction catalyst depends on variousfactors including the type of catalyst selected and the choice of theremaining components in the composition, however the amount of thecondensation reaction catalyst may range from 0.001% to 5% based on theweight of the reactive resin and polymer (II).

Suitable condensation reaction catalyst may be a Lewis acid; a primary,secondary, or tertiary organic amine; a metal oxide; a titaniumcompound; a tin compound; a zirconium compound; or a combinationthereof. The condensation reaction catalyst may comprise a carboxylicacid salt of a metal ranging from lead to manganese inclusive in theelectromotive series of metals. Alternatively, the condensation reactioncatalyst may comprise a chelated titanium compound, a titanate such as atetraalkoxytitanate, a titanium ester, or a combination thereof.Examples of suitable titanium compounds include, but are not limited to,diisopropoxytitanium bis(ethylacetoacetate), tetrabutoxy titanate,tetrabutyltitanate, tetraisopropyltitanate, andbis-(ethoxyacetoacetonate)diisopropoxy titanium (IV), and a combinationthereof. Alternatively the condensation reaction catalyst may comprise atin compound such as dibutyltin diacetate; dibutyltin dilaurate; dibutyltin oxide; stannous octoate; tin oxide; a titanium ester, such astetrabutyl titanate, tetraethylhexyl titanate and tetraphenyltitanate; asiloxytitanate, such as tetrakis(trimethylsiloxy)titanium andbis(trimethylsiloxy)-bis(isopropoxy)titanium; and abetadicarbonyltitanium compound, such as bis(acetylacetonyl)diisopropyltitanate; or a combination thereof. Alternatively, the condensationreaction catalyst may comprise an amine, such as hexylamine; or anacetate or quat salt of an amine.

Component (V) is a crosslinker. The type and amount of crosslinker willdepend on various factors including the type and amount of curablegroups based on the reactive resin and polymer (II).

In certain embodiments, the crosslinker is a condensation reactioncrosslinker that may be selected from, for example, trialkoxysilanesexemplified by propyltrimethoxysilane, phenyltrimethoxysilane,glycidoxypropyltrimethoxysilane, ethyltrimethoxysilane,aminopropyltrimethoxysilane, aminoethylaminopropyltrimethoxysilane,methyltrimethoxysilane, phenyl trimethoxysilane, andmethyltriethoxysilane; acetoxysilanes such as methyltriacetoxysilane orethyltriacetoxysilane; ketoximosilanes such asmethyltri(methylethylketoximo)silane, tetra(methylethylketoximo)silane,methyltris(methylethylketoximo)silane, andvinyltris(methylethylketoximo) silane; alkyl orthosilicates such astetraethyl orthosilicate, tetramethoxysilane, tetraethoxysilane, andcondensation products of these orthosilicates, which are typicallyreferred to as alkyl polysilicates; methylvinyl bis(n-methylacetamido)silane; and a combination thereof.

In certain embodiments, the amount of crosslinker utilized in thesilicone adhesive composition is dependent upon numerous factors, but isbased primarily upon the type and amount of curable groups contained incomponents (I) and (II). In certain embodiments, the amount ofcrosslinker is from 0.1 to 10 weight percent, such as from 0.5 to 3weight percent, based upon the total weight of the reactive resin andpolymer (II).

The curable silicone composition may optionally further comprise one ormore additional components. The additional components are exemplified by(VI) a solvent, (VII) an adhesion promoter, (VIII) a colorant, (IX) areactive diluent, (X) a corrosion inhibitor, (XI) a polymerizationinhibitor, and a combination thereof. The curable silicone compositionmay optionally further comprise (XII) a filler, (XIII) a filler treatingagent, (XIV) an acid acceptor; and a combination thereof, for example,if a filler f) has not been added during the process for making theclustered functional polyorganosiloxane, or if more or a differentfiller is desired to formulate, e.g., the filler (XII) to be added is athermally conductive filler, described below.

Component (VI) is a solvent. Suitable solvents are exemplified byorganic solvents such as toluene, xylene, acetone, methylethylketone,methyl isobutyl ketone, hexane, heptane, alcohols such as decyl alcoholor undecyl alcohol, and a combination thereof; and non-crosslinkablesilicone solvents such as trimethylsiloxy-terminatedpolydimethylsiloxanes, trimethylsiloxy-terminatedpolymethylphenylsiloxanes, and a combination thereof. Examples ofsilicone solvents are known in the art and are commercially available,for example, as Dow Corning® OS Fluids from Dow Corning Corporation ofMidland, Mich., U.S.A. The amount of component (IV) may range from0.001% to 90% based on the weight of the curable silicone composition.

Component (VII) is an adhesion promoter. Examples of suitable adhesionpromoters include an alkoxysilane such as an epoxy-functionalalkoxysilane, or a mercapto-functional compound; a combination of analkoxysilane and a hydroxy-functional polyorganosiloxane; amercapto-functional compound; an unsaturated compound; anepoxy-functional silane; an epoxy-functional siloxane; a combination,such as a reaction product, of an epoxy-functional silane orepoxy-functional siloxane and a hydroxy-functional polyorganosiloxane;or a combination thereof. Suitable adhesion promoters are known in theart and are commercially available. For example, Silquest® A186 isbeta-(3,4-epoxycyclohexyl)ethyltrimethoxysilane which is commerciallyavailable from Crompton OSi Specialties of Middlebury, Conn., USA.CD9050 is a monofunctional acid ester useful as an adhesion promoterthat provides adhesion to metal substrates and is designed for radiationcurable compositions. CD9050 is commercially available from Sartomer Co.SR489D is tridecyl acrylate, SR395 is isodecyl acrylate, SR257 isstearyl acrylate, SR506 is isobornyl acrylate, SR833S is tricyclodecanedimethanol diacrylate, SR238 is 1,6 hexanediol diacrylate, and SR351 istrimethylol propane triacrylate, all of which are also commerciallyavailable from Sartomer Co. The amount of adhesion promoter added to thecomposition depends on various factors including the specific adhesionpromoter selected, the other components of the composition, and the enduse of the composition, however, the amount may range from 0.1% to 5%based on the weight of the composition. Other suitable adhesionpromoters, which are useful to promote adhesion to metals, includemaleic anhydride, methacrylic anhydride, and glycidyl methacrylate.

Component (VII) can be an unsaturated or epoxy-functional compound.Suitable epoxy-functional compounds are known in the art andcommercially available, see for example, U.S. Pat. Nos. 4,087,585;5,194,649; 5,248,715; and 5,744,507 (at col. 4-5). Component (g) maycomprise an unsaturated or epoxy-functional alkoxysilane. For example,the functional alkoxysilane can have the formula R²⁰ _(v)Si(OR²¹)_((4-v)), where subscript v is 1, 2, or 3, alternatively v is 1.

Each R²⁰ is independently a monovalent organic group with the provisothat at least one R²⁰ is an unsaturated organic group or anepoxy-functional organic group. Epoxy-functional organic groups for R²⁰are exemplified by 3-glycidoxypropyl and (epoxycyclohexyl)ethyl.Unsaturated organic groups for R²⁰ are exemplified by3-methacryloyloxypropyl, 3-acryloyloxypropyl, and unsaturated monovalenthydrocarbon groups such as vinyl, allyl, hexenyl, undecylenyl.

Each R²¹ is independently an unsubstituted, saturated hydrocarbon groupof 1 to 4 carbon atoms, alternatively 1 to 2 carbon atoms. R²¹ isexemplified by methyl, ethyl, propyl, and butyl.

Examples of suitable epoxy-functional alkoxysilanes include3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane,(epoxycyclohexyl)ethyldimethoxysilane,(epoxycyclohexyl)ethyldiethoxysilane and combinations thereof. Examplesof suitable unsaturated alkoxysilanes include vinyltrimethoxysilane,allyltrimethoxysilane, allyltriethoxysilane, hexenyltrimethoxysilane,undecylenyltrimethoxysilane, 3-methacryloyloxypropyl trimethoxysilane,3-methacryloyloxypropyl triethoxysilane, 3-acryloyloxypropyltrimethoxysilane, 3-acryloyloxypropyl triethoxysilane, and combinationsthereof. Alternatively, examples of suitable adhesion promoters includeglycidoxypropyltrimethoxysilane and a combination ofglycidoxypropyltrimethoxysilane with an aluminum chelate or zirconiumchelate.

Component (VII) may comprise an epoxy-functional siloxane such as areaction product of a hydroxy-terminated polyorganosiloxane with anepoxy-functional alkoxysilane, as described above, or a physical blendof the hydroxy-terminated polyorganosiloxane with the epoxy-functionalalkoxysilane. Component (VII) may comprise a combination of anepoxy-functional alkoxysilane and an epoxy-functional siloxane. Forexample, component (VII) is exemplified by a mixture of3-glycidoxypropyltrimethoxysilane and a reaction product ofhydroxy-terminated methylvinylsiloxane with3-glycidoxypropyltrimethoxysilane, or a mixture of3-glycidoxypropyltrimethoxysilane and a hydroxy-terminatedmethylvinylsiloxane, or a mixture of 3-glycidoxypropyltrimethoxysilaneand a hydroxy-terminated methylvinyl/dimethylsiloxane copolymer. Whenused as a physical blend rather than as a reaction product, thesecomponents may be stored separately in multiple-part kits.

Suitable mercapto-functional compounds include an organomercaptan, amercapto containing silane, or a combination thereof. Suitable mercaptocontaining silanes include 3-mercaptopropyltrimethoxysilane. Suitablemercapto-functional compounds are disclosed in U.S. Pat. No. 4,962,076.One skilled in the art would recognize that certain components describedherein may be added to the composition for more than one or differentpurposes. For example, alkoxysilanes may be use as adhesion promoters,filler treating agents, and/or as crosslinking agents in condensationreaction curable silicone compositions.

Component (VIII) is a colorant (e.g., dye or pigment). Examples ofsuitable colorants include carbon black, Stan-Tone 40SP03 Blue (which iscommercially available from PolyOne) and Colorant BA 33 Iron Oxidepigment (which is commercially available from Cathay Pigments (USA),Inc. Valparaiso, Ind. 46383 USA). Examples of colorants are known in theart and are disclosed in U.S. Pat. Nos. 4,962,076; 5,051,455; and5,053,442. The amount of colorant added to the curable siliconecomposition depends on various factors including the other components ofthe composition, and the type of colorant selected, however, the amountmay range from 0.001% to 20% based on the weight of the composition.

Component (IX) is a reactive diluent. Component (IX) may be diluent thatreacts with a functional group on component (I) or (II). The reactivediluent may be a monofunctional reactive diluent, a difunctionalreactive diluent, a polyfunctional reactive diluent, or a combinationthereof. The reactive diluent selected will depend on various factorsincluding the curable groups on components (I) and (II). However,examples of suitable reactive diluents include an acrylate, an anhydridesuch as a maleic anhydride or methacrylic anhydride, an epoxy such as amonofunctional epoxy compound, a methacrylate such as glycidylmethacrylate, an oxetane, a vinyl acetate, a vinyl ester, a vinyl ether,a fluoro alkyl vinyl ether, a vinyl pyrrolidone such as N-vinylpyrrolidone, a styrene, or a combination thereof.

Mono-functional acrylate and methacrylate esters are commerciallyavailable from companies such as Sartomer, Rohm Haas, Hitachi Chemical,Arkema, Inc., Cytec, Sans Ester Corp, Rahn, and Bomar Specialties Co.Specific examples include methyl acrylate; methyl methacrylate; ethylacrylate; ethyl methacrylate; butyl acrylate; butyl methacrylate;cyclohexyl acrylate; hexyl acrylate; 2-ethylhexyl acrylate; isodecylmethacrylate; isobornyl methacrylate; hydroxyethyl methacrylate;hydroxypropyl acrylate; hydroxypropyl methacrylate; n-octyl acrylate;cyclohexyl methacrylate; hexyl methacrylate; 2-ethylhexyl methacrylate;decyl methacrylate; dodecyl methacrylate; lauryl acrylate; tert-butylmethacrylate; acrylamide; N-methyl acrylamide; diacetone acrylamide;N-tert-butyl acrylamide; N-tert-octyl acrylamide; N-butoxyacrylamide;gamma-methacryloxypropyl trimethoxysilane; dicyclopentadienyloxyethylmethacrylate; 2-cyanoethyl acrylate; 3-cyanopropyl acrylate;tetrahydrofurfuryl methacrylate; tetrahydrofurfuryl acrylate; glycidylacrylate; acrylic acid; methacrylic acid; itaconic acid; glycidylmethacrylate; 1,12 dodecanediol dimethacrylate; 1,3-butylene glycoldiacrylate; 1,3-butylene glycol dimethacrylate; 1,3-butylene glycoldimethacrylate; 1,4-butanediol diacrylate; 1,4-butanedioldimethacrylate; 1,4-butanediol dimethacrylate; 1,6 hexanedioldiacrylate; 1,6 hexanediol dimethacrylate; alkoxylated cyclohexanedimethanol diacrylate; alkoxylated hexanediol diacrylate; alkoxylatedneopentyl glycol diacrylate; cyclohexane dimethanol diacrylate;cyclohexane dimethanol dimethacrylate; diethylene glycol diacrylate;diethylene glycol dimethacrylate; dipropylene glycol diacrylate;ethoxylated bisphenol a diacrylate; ethoxylated bisphenol adimethacrylate; ethylene glycol dimethacrylate; neopentyl glycoldiacrylate; neopentyl glycol dimethacrylate; polypropyleneglycoldimethacrylate; propoxylated neopentyl glycol diacrylate;propoxylated neopentyl glycol diacrylate; tricyclodecane dimethanoldiacrylate; triethylene glycol diacrylate; trimethylolpropanetriacrylate; trimethylolpropane trimethacrylate; tris(2-hydroxy ethyl)isocyanurate triacrylate; tris(2-hydroxy ethyl) isocyanuratetriacrylate; n,n′-m-phenylenedimaleimide; triallyl cyanurate; triallylisocyanurate; metallic diacrylate; metallic dimethacrylate; metallicmonomethacrylate; metallic diacrylate (difunctional); metallicdimethacrylate (difunctional); triethoxysilylpropyl methacrylate;tributoxysilylpropyl methacrylate; dimethoxymethylsilylpropylmethacrylate; diethoxymethylsilylpropyl methacrylate;dibutoxymethylsilylpropyl methacrylate; diisopropoxymethylsilylpropylmethacrylate; dimethoxysilylpropyl methacrylate; diethoxysilylpropylmethacrylate; dibutoxysilylpropyl methacrylate; diisopropoxysilylpropylmethacrylate; trimethoxysilylpropyl acrylate; triethoxysilylpropylacrylate; tributoxysilylpropyl acrylate; dimethoxymethylsilylpropylacrylate; diethoxymethylsilylpropyl acrylate; dibutoxymethylsilylpropylacrylate; diisopropoxymethylsilylpropyl acrylate; dimethoxysilylpropylacrylate; diethoxysilylpropyl acrylate; dibutoxysilylpropyl acrylate;and diisopropoxysilylpropyl acrylate.

Examples of suitable vinyl ethers include, but are not limited tobutanediol divinyl ether, cyclohexanedimethanol divinyl ether,cyclohexanedimethanol monovinyl ether, cyclohexyl vinyl ether,diethyleneglycol divinyl ether, diethyleneglycol monovinyl ether,dodecyl vinyl ether, ethyl vinyl ether, hydroxybutyl vinyl ether,isobutyl vinyl ether, isopropyl vinyl ether, n-butyl vinyl ether,n-propyl vinyl ether, octadecyl vinyl ether, triethyleneglycol divinylether, and combinations thereof. Vinyl ethers are known in the art andcommercially available from BASF AG of Germany, Europe. The amount ofcomponent (IX) depends on various factors such as the specific reactivediluent selected, but the amount may range from 0.5 to 50% based on theweight of curable silicone composition. One skilled in the art wouldrecognize that some of the reactive diluents described herein (such asthe difunctional and polyfunctional acrylates and methacrylates) mayalso be used in addition to, or instead of, the reactive speciesdescribed above as component c) of (I).

Component (X) is a corrosion inhibitor. Examples of suitable corrosioninhibitors include benzotriazole, mercaptabenzotriazole,mercaptobenzothiazole, and commercially available corrosion inhibitorssuch as 2,5-dimercapto-1,3,4-thiadiazole derivative (CUVAN® 826) andalkylthiadiazole (CUVAN® 484) from R. T. Vanderbilt. The amount ofcomponent (X) may range from 0.05% to 0.5% based on the weight of thecurable silicone composition.

Component (XI) is a polymerization inhibitor. Examples of suitablepolymerization inhibitors for acrylate and methacrylate curable groupsinclude, but are not limited to:2,6,-Di-tert-butyl-4-(dimethylaminomethyl)phenol (DBAP), hydroquinone(HQ); 4-methoxyphenol (MEHQ); 4-ethoxyphenol; 4-propoxyphenol;4-butoxyphenol; 4-heptoxyphenol; butylated hydroxytoluene (BHT);hydroquinone monobenzylether; 1,2-dihydroxybenzene; 2-methoxyphenol;2,5-dichlorohydroquinone; 2,5-di-tert-butylhydroquinone;2-acetylhydroquinone; hydroquinone monobenzoate; 1,4-dimercaptobenzene;1,2-dimercaptobenzene; 2,3,5-trimethylhydroquinone; 4-aminophenol;2-aminophenol; 2-N, N-dimethylaminophenol; 2-mercaptophenol;4-mercaptophenol; catechol monobutylether; 4-ethylaminophenol;2,3-dihydroxyacetophenone; pyrogallol-1,2-dimethylether;2-methylthiophenol; t-butyl catechol; di-tert-butylnitroxide;di-tert-amylnitroxide; 2,2,6,6-tetramethyl-piperidinyloxy;4-hydroxy-2,2,6,6-tetramethyl-piperidinyloxy;4-oxo-2,2,6,6-tetramethyl-piperidinyloxy;4-dimethylamino-2,2,6,6-tetramethyl-piperidinyloxy;4-amino-2,2,6,6-tetramethyl-piperidinyloxy;4-ethanoloxy-2,2,6,6-tetramethyl-piperidinyloxy;2,2,5,5-tetramethyl-pyrrolidinyloxy;3-amino-2,2,5,5-tetramethyl-pyrrolidinyloxy;2,2,5,5-tetramethyl-1-oxa-3-azacyclopentyl-3-oxy;2,2,5,5-tetramethyl-3-pyrrolinyl-1-oxy-3-carboxylic acid;2,2,3,3,5,5,6,6-octamethyl-1,4-diazacyclohexyl-1,4-dioxy; salts of4-nitrosophenolate; 2-nitrosophenol; 4-nitrosophenol; copperdimethyldithiocarbamate; copper diethyldithiocarbamate; copperdibutyldithiocarbamate; copper salicylate; methylene blue; iron;phenothiazine (PTZ); 3-oxophenothiazine; 5-oxophenothiazine;phenothiazine dimer; 1,4-benzenediamine;N-(1,4-dimethylpentyl)-N′-phenyl-1,4-benzenediamine;N-(1,3-dimethylbutyl)-N′-phenyl-1,4-benzenediamine;N-nitrosophenylhydroxylamine and salts thereof; nitric oxide;nitrobenzene; p-benzoquinone; pentaerythrityltetrakis(3-laurylthiopropionate); dilauryl thiodipropionate; distearyllthiodipropionate; ditridecyl thiodipropionate; tetrakis[methylene3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]methane; thiodiethylenebis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate];octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate;isotridecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate;N,N′-hexamethyl(3,5-di-tertbutyl-4-hydroxyhydrocinnamamide);iso-octyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate;2,2′-ethylidenebis-(4,6-di-tert-butylphenol);1,3,5-trimethyl-2,4,6-tris(3,5-di-tert-butyl-4-hydroxybenzyl)benzene;4,6-bis(octylthiomethyl)-o-cresol; triethyleneglycol-bis-3-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionate;tris-(3,5-di-tert-butylhydroxybenzyl) isocyanurate;tris(2,4-di-tert-butylphenyl)phosphate; distearyl pentaerythritoldiphosphite; bis(2,4-di-tert-butyl phenyl)pentaerythritol diphosphite;2,5-di-tert-amyl-hydroquinone; or isomers thereof; combinations of twoor more thereof; or combinations of one or more of the above withmolecular oxygen. When present, the polymerization inhibitor may beadded to the curable silicone composition in an amount ranging from 100ppm to 4,000 ppm. Polymerization inhibitors are known in the art and aredisclosed, for example in EP 1 359 137.

Component (XII) is a filler that may be added if a filler was not usedin the process for making the clustered functional polyorganosiloxane,or if additional filler or a different type of filler is desired, suchas a thermally conductive filler. The filler may be a filler describedabove as component e). Alternatively, the filler may be a thermallyconductive filler.

The thermally conductive filler may be both thermally conductive andelectrically conductive. Alternatively, the thermally conductive fillermay be thermally conductive and electrically insulating. The thermallyconductive filler may be selected from the group consisting of aluminumnitride, aluminum oxide, aluminum trihydrate, barium titanate, berylliumoxide, boron nitride, carbon fibers, diamond, graphite, magnesiumhydroxide, magnesium oxide, metal particulate, onyx, silicon carbide,tungsten carbide, zinc oxide, and a combination thereof. The thermallyconductive filler may comprise a metallic filler, an inorganic filler, ameltable filler, or a combination thereof. Metallic fillers includeparticles of metals and particles of metals having layers on thesurfaces of the particles. These layers may be, for example, metalnitride layers or metal oxide layers on the surfaces of the particles.Suitable metallic fillers are exemplified by particles of metalsselected from the group consisting of aluminum, copper, gold, nickel,silver, and combinations thereof, and alternatively aluminum. Suitablemetallic fillers are further exemplified by particles of the metalslisted above having layers on their surfaces selected from the groupconsisting of aluminum nitride, aluminum oxide, copper oxide, nickeloxide, silver oxide, and combinations thereof. For example, the metallicfiller may comprise aluminum particles having aluminum oxide layers ontheir surfaces.

Inorganic fillers are exemplified by onyx; aluminum trihydrate, metaloxides such as aluminum oxide, beryllium oxide, magnesium oxide, andzinc oxide; nitrides such as aluminum nitride and boron nitride;carbides such as silicon carbide and tungsten carbide; and combinationsthereof. Alternatively, inorganic fillers are exemplified by aluminumoxide, zinc oxide, and combinations thereof. Meltable fillers maycomprise Bi, Ga, In, Sn, or an alloy thereof. The meltable filler mayoptionally further comprise Ag, Au, Cd, Cu, Pb, Sb, Zn, or a combinationthereof. Examples of suitable meltable fillers include Ga, In—Bi—Snalloys, Sn—In—Zn alloys, Sn—In—Ag alloys, Sn—Ag—Bi alloys, Sn—Bi—Cu—Agalloys, Sn—Ag—Cu—Sb alloys, Sn—Ag—Cu alloys, Sn—Ag alloys, Sn—Ag—Cu—Znalloys, and combinations thereof. The meltable filler may have a meltingpoint ranging from 50° C. to 250° C., alternatively 150° C. to 225° C.The meltable filler may be a eutectic alloy, a non-eutectic alloy, or apure metal. Meltable fillers are commercially available.

For example, meltable fillers may be obtained from Indium Corporation ofAmerica, Utica, N.Y., U.S.A.; Arconium, Providence, R.I., U.S.A.; andAIM Solder, Cranston, R.I., U.S.A. Aluminum fillers are commerciallyavailable, for example, from Toyal America, Inc. of Naperville, Ill.,U.S.A. and Valimet Inc., of Stockton, Calif., U.S.A. Silver filler iscommercially available from Metalor Technologies U.S.A. Corp. ofAttleboro, Mass., U.S.A.

Thermally conductive fillers are known in the art and commerciallyavailable, see for example, U.S. Pat. No. 6,169,142 (col. 4, lines7-33). For example, CB-A20S and Al-43-Me are aluminum oxide fillers ofdiffering particle sizes commercially available from Showa-Denko, andAA-04, AA-2, and AA18 are aluminum oxide fillers commercially availablefrom Sumitomo Chemical Company Zinc oxides, such as zinc oxides havingtrademarks KADOX® and XX®, are commercially available from ZincCorporation of America of Monaca, Pa., U.S.A.

The shape of the thermally conductive filler particles is notspecifically restricted, however, rounded or spherical particles mayprevent viscosity increase to an undesirable level upon high loading ofthe thermally conductive filler in the composition.

The thermally conductive filler may be a single thermally conductivefiller or a combination of two or more thermally conductive fillers thatdiffer in at least one property such as particle shape, average particlesize, particle size distribution, and type of filler. For example, itmay be desirable to use a combination of inorganic fillers, such as afirst aluminum oxide having a larger average particle size and a secondaluminum oxide having a smaller average particle size. Alternatively, itmay be desirable, for example, use a combination of an aluminum oxidehaving a larger average particle size with a zinc oxide having a smalleraverage particle size. Alternatively, it may be desirable to usecombinations of metallic fillers, such as a first aluminum having alarger average particle size and a second aluminum having a smalleraverage particle size. Alternatively, it may be desirable to usecombinations of metallic and inorganic fillers, such as a combination ofaluminum and aluminum oxide fillers; a combination of aluminum and zincoxide fillers; or a combination of aluminum, aluminum oxide, and zincoxide fillers. Use of a first filler having a larger average particlesize and a second filler having a smaller average particle size than thefirst filler may improve packing efficiency, may reduce viscosity, andmay enhance heat transfer.

The average particle size of the thermally conductive filler will dependon various factors including the type of thermally conductive fillerselected and the exact amount added to the curable silicone composition,as well as the bondline thickness of the device in which the curedproduct of the composition will be used when the cured product will beused as a thermal interface material (TIM). However, the thermallyconductive filler may have an average particle size ranging from 0.1micrometer to 80 micrometers, alternatively 0.1 micrometer to 50micrometers, and alternatively 0.1 micrometer to 10 micrometers.

The amount of the thermally conductive filler in the composition dependson various factors including the cure mechanism selected for the curablesilicone composition and the specific thermally conductive fillerselected. However, the amount of the thermally conductive filler mayrange from 30 vol % to 80 vol %, alternatively 50 vol % to 75 vol % byvolume of the composition. Without wishing to be bound by theory, it isthought that when the amount of filler is greater than 80 vol %, thecomposition may crosslink to form a cured silicone with insufficientdimensional integrity for some applications, and when the amount offiller is less than 30%, the cured silicone prepared from thecomposition may have insufficient thermal conductivity for TIMapplications.

Component (XIII) is a filler treating agent. The filler treating agentmay be a filler treating agent described above as the filler treatingagent for component e). Alternatively, metal fillers can be treated withalkylthiols such as octadecyl mercaptan and others, and fatty acids suchas oleic acid, stearic acid, titanates, titanate coupling agents,zirconate coupling agents, and a combination thereof.

Filler treating agents for alumina or passivated aluminum nitride mayinclude alkoxysilyl functional alkylmethyl polysiloxanes (e.g., partialhydrolysis condensate of R²² _(w)R²³ _(x)Si(OR)_((4w-x)) or cohydrolysiscondensates or mixtures), or similar materials where the hydrolyzablegroup may comprise silazane, acyloxy or oximo. In all of these, a grouptethered to Si, such as R²² in the formula above, is a long chainunsaturated monovalent hydrocarbon or monovalent aromatic-functionalhydrocarbon. Each R²³ is independently a monovalent hydrocarbon group,and each R²⁴ is independently a monovalent hydrocarbon group of 1 to 4carbon atoms. In the formula above, subscript w is 1, 2, or 3 andsubscript x is 0, 1, or 2, with the proviso that the sum (w+x) is 1, 2,or 3. One skilled in the art would recognize that the alkoxysilanes andmercapto-functional compounds described as adhesion promoters forcomponent (VII) may alternatively be used, in addition to or instead of,filler treating agents for component (XIII). One skilled in the artcould optimize a specific treatment to aid dispersion of the fillerwithout undue experimentation.

Component (XIV) is an acid acceptor. The acid acceptor may comprise ametal oxide such as magnesium oxide. Acid acceptors are known in the artand are commercially available under tradenames including Rhenofit F,Star Mag CX-50, Star Mag CX-150, BLP-3, and MaxOx98LR. Rhenofit F wascalcium oxide from Rhein Chemie Corporation of Chardon, Ohio, USA. StarMag CX-50 was magnesium oxide from Merrand International Corp. ofPortsmouth, N.H., USA. MagOX 98LR was magnesium oxide from PremierChemicals LLC of W. Conshohocken, Pa., USA. BLP-3 was calcium carbonatewas Omya Americas of Cincinnati, Ohio, USA.

The curable silicone composition of the present invention is generallyformed by a dry blend process, in which the clustered functionalpolyorganosiloxane (I), the reactive resin and polymer (II), the radicalinitiator (III), the moisture cure initiator (IV); and the crosslinker(IV), as well as any combination of the optional components (VI)-XIV),are mixed in a container prior to application. In certain embodiments,the dry blend process occurs in an inert atmosphere (using 2% oxygen innitrogen atmosphere) to enable the polymerization inhibitor (XI) and toprevent premature radical formation.

The curable silicone composition described above may be used in variousapplications including, for example, sealant applications such asforming a lid seal (e.g., automotive lid seal or microelectronics lidseal), forming an adhesive (such as a die attach adhesive or thermallyconductive adhesives), or forming a terminal sealant. One skilled in theart would be able to select appropriate curing agents and additionalcomponents to formulate compositions for sealants and adhesives based onthe description above and the examples provided herein.

The curable silicone composition described above, and a cured siliconecoating prepared by curing the composition on a substrate, are useful inelectronics applications, including both microelectronics andmacroelectronics applications as well as optoelectronics applicationsand thermally conductive electronics applications, such as makingthermally conductive adhesives. Cured silicone adhesives prepared fromsuch a curable silicone composition may adhere to various substratessuch as electronics substrates, including metal substrates such as gold,silver, aluminum, copper, and electroless nickel; as well as polymericsubstrates such as FR4, Nylon, polycarbonate, Lucite (which ispolymethylmethacrylate, PMMA), polybutylene terephthalate (PBT), andliquid crystal polymers such as Xydar®, available from Solvay Chemicals,Houston, Tex. 77098 USA.

The curable silicone compositions described above may be dispensed orotherwise applied to an appropriate substrate at a desired thickness andcured by thermal radical cure and moisture cure. The curing stepincludes the step of heating the applied composition to promote theradical curing of the radical group containing components of the curablesilicone composition. In addition, any moisture or condensation presentwill promote the moisture curing of the moisture cure group containingcomponents. More specific examples of the curing are provided in theExamples below.

EXAMPLES

These examples are intended to illustrate the invention to one ofordinary skill in the art and should not be interpreted as limiting thescope of the invention set forth in the claims. The following componentswere used in the examples described below.

NMR: Solution-state ²⁹Si- and ¹³C-NMR spectra were recorded on a MercuryVX 400 MHz spectrometer at room temperature (20-22° C.) using CDCl3(Isotec) in a 16 mm Si-free probe. Cr(acac)₃ (20 mM) was added to NMRsamples as a relaxation agent. ²⁹Si NMR spectra were acquired at 79.493MHz and processed with 5 Hz of Lorentzian line broadening. The spectrawere only semiquantitative due to the long relaxation times of the ²⁹Sinucleus, but relative comparison of spectra acquired under identicalconditions was considered quantitative. ¹³C NMR spectra were acquired at100.626 MHz and processed with 3 Hz of Lorentzian line broadening. Forboth nuclei, 256-512 scans with a 90° pulse width were typicallyco-added to achieve adequate sensitivity; a 6-second (²⁹Si) or 12-second(13C) delay between pulses was used. Gated decoupling was used to removenegative nuclear Overhauser effects. Chemical shifts were referenced toexternal tetramethylsilane (TMS).

I. Impact of Isomer Reducing Agent on Clustered FunctionalPolyorganosiloxane

A. Variation in Amount of Added Isomer Reducing Agent on Generation ofT(Oz) and D(Oz) Units

In a dry 3-neck flask, 100 g DOW CORNING® SFD-119(dimethylvinyl-terminated dimethyl siloxane), 6.2 g cyclicmethylhydrogensiloxane, 14 g allyl methacrylate (AMA), 0.2 g butylatedhydroxytoluene (BHT) and varying amounts of an isomer reducing agent(either OFS-1579, available from Dow Corning Corporation of Midland,Mich., or DBAP (2,6-Di-tert-butyl-4-(dimethylaminomethyl)phenol) wereadded and mixed under a nitrogen blanket. 0.12 g of a platinum catalyst(DOW CORNING® 2-0707) was added and the mixture was mixed for anadditional 5 minutes. The mixture was then heated to 60° C. for 1 hour.The reaction was monitored by the reduction in the SiH peak at 2173 cm⁻¹by IR spectroscopy. The mixture was cooled to room temperature anddiallyl maleate (DAM) was added. The reaction mixture was analyzed by²⁹Si NMR for the presence of T(Oz) and D(Oz) units. The results aresummarized in Tables 1 and 2 below and indicate that the introduction ofat least 100 ppm of an isomer reducing agent in the formulation (eitherOFS-1579 or DBAP) reduced the level of T(Oz) and D(Oz) units by at least10%, which corresponds to at least a 10% reduction in the beta-additionof SiH groups of the methylhydrogensiloxane to the allyl methacrylate.

TABLE 1 OFS-1579 (ppm) 0 100 200 500 1000 T(Oz) 0.46 0.39 0.43 0.29 0.27D(Oz) 1.81 1.42 1.38 1.49 1.36 % Decrease in Isomer 0 20.3 20.3 21.628.2

TABLE 2 DBAP (ppm) 0 100 200 500 1000 T(Oz) 0.46 0.34 0.37 0.16 0.27D(Oz) 1.81 1.68 1.65 1.59 1.6 % Decrease in Isomer 0 11.0 11.0 22.9 17.6

B. Viscosity Comparison of Samples with and without Isomer ReducingAgent (Samples 1 and 2)

In a 10 liter Turello mixer, 5000 g of DOW CORNING® SFD117, 196.34 g ofcyclic methylhydrogensiloxane, 467.76 g of AMA and 1.13 g of BHT wereadded and mixed for 15 minutes. 5.45 g of platinum catalyst was addedand the mixture was mixed for a further 15 minutes at room temperature.The mixture was heated to 80° C. for 1 hour, wherein samples wereevaluated by IR for the disappearance of SIH signal. At 1 hour themixture was cool to less than 45° C. wherein 11.33 g of DAM was added.The vacuum was set to 55 mmHg and the temperature was increased to 80°C. and the mixture was stripped for 30 minutes. The resultantcomposition (Sample 1) was cooled to less than 30° before packaging.

In a 10 liter Turello mixer, 5000 g of DOW CORNING® SFD117, 196.34 g ofcyclic methylhydrogensiloxane, 467.76 g of AMA, 1.13 g of BHT and 1.13 gof OFS-1579 were added and mixed for 15 minutes. 5.45 g of platinumcatalyst was added and the mixture was mixed for a further 15 minutes atroom temperature. The mixture was heated to 80° C. for 1 hour, whereinsamples were evaluated by IR for the disappearance of SIH signal. At 1hour the mixture was cool to less than 45° C. wherein 11.33 g of DAM wasadded. The vacuum was set to 55 mmHg and the temperature was increasedto 80° C. and the mixture was stripped for 30 minutes. The resultantcomposition (Sample 2) was cooled to less than 30° before packaging.

Samples 1 and 2 were measured for viscosity (in centipoises (cps) usinga Brookfield LVF viscometer at 3 revolutions per minute using a #3spindle. The results, as shown in Table 3, that the introduction of theisomer reducing agent (Sample 2) provided a relatively stable viscosityover a 194 day period, while the viscosity of the corresponding example(Sample 1) without the isomer reducing agent increased to almost doublethe viscosity after 127 days and to the point of gellation after 194days.

TABLE 3 Days of aging Initial 127 194 Sample 2 9200 9600 9600 Sample 16800 11600 GelledII. Evaluation of Physical Properties of Adhesive Composition

A. Preparation of Methacrylate Clustered Silicone Polymers with (MCP-1)and without (MCP) Isomer Reducing Agent.

In a 50 liter Turello mixer 12 kg of a silicone polymer masterbatch(MB2030) (SFD-128/silica blend), 6.77 kg of SFD120 polymer, 1.12 kg ofOS20 silicone fluid (methylsiloxane fluid available from Dow CorningCorporation of Midland, Mich.) and 20.45 g of OFS-1579 isomer reducingagent were loaded. The mixture was inserted using 2% oxygen in nitrogenatmosphere and stirred for 15 minutes. To this homogenized mixture wasadded 6 g of BHT, 409.7 g of cyclic methylhydrogensiloxane, and 965.3 gof AMA. The resultant mixture was stirred for an additional 20 minutesat room temperature, at which point 26.62 g of a platinum catalyst wasadded and the mixture. The mixture was stirred for 10 additional minutesbefore setting the temperature at 60° C. The temperature was held for 30minutes at 60° C. before cooling to greater than 40° C. and adding 26.62g of DAM. The mixture was then cooled to less than 35° C. before adding182.8 g of methyltrimethoxysilane (MTM). The mixture was then heated to60° C. and held for 30 minutes, wherein the temperature was increased to80° C. and a vacuum of 55 mm Hg was applied for 40 minutes. Theresultant polymer is hereinafter referred to as MCP-1.

For producing the MCP resin without an isomer reducing agent, the sameprocedure was followed as in the previous paragraph with the exceptionof the addition of 20.45 g of OFS-1579 isomer reducing agent.

B. Synthesis Alkoxylated Resin Polymer Blend (ARPB-1)

To a 10 kg Turello mixer a resin polymer blend (RPB) was added alongwith magnesium oxide, and iron pigment BA33 and blended for 15 minutesunder a nitrogen blanket. To this mixer a mixture ofmethyltrimethoxysilane (DOW CORNING® Z-6070) and hexamethyldisilazane(DOW CORNING® 4-2839) was added. The mixture was blended for 15 minutesprior to steam heating the material to 60-80° C. The temperature washeld at 60° C. for 30 minutes. The temperature was increased to 120° C.and a fully vacuum of less than 50 torr was applied for 60 minutes. Themixture was cooled to less than 40° C. prior to the addition of analkoxylating agent (ETM polymer—DOW CORNING® XCF3-6105) and endcapper(Bis H DOW CORNING® 2-5161). After 15 minutes of mixing a platinumcatalyst was added with a further 15 minutes of mixing prior to heatingthe mixture to a temperature of 75-90° C. The SiH/CH₃ ratio wasmonitored by IR until completion of the reaction within 20 minutes. Thematerial was devolatilized by heating to 125° C. with full vacuum of 55mm Hg for 30 minutes.

C. Preparation of Adhesives and Adhesive Testing

Adhesive compositions were prepared by cold blending the methacrylateclustered silicone polymer with and without an isomer reducing agent(i.e., MCP-1 and MCP, respectively) with ARPB-1 and with additionpromoter packages and radical initiators as provided in Table 4 below.The resultant adhesive compositions were then evaluated for viscosity at1 day, 7 days and 14 days as shown in Table 5.

TABLE 4 MCP or MCP-1 71.75 ARBP-1 19.34 RBM-9020 Modifier¹ 2.95 OFS-6030Silane² 1.97 TAIC³ 0.49 TYZOR TNBT⁴ 0.62 A-1110⁵ 0.1 A186⁶ 0.62-Mercaptobenzothiazole⁷ 0.15 OFS-2306 Silane⁸ 1.96 OFS-1719 Silane⁹ 0.1TINOPAL OB¹⁰ 0.02 ¹T-catalyst available from Dow Corning Corporation ofMidland, Michigan. ²Methacryloxypropyltrimethoxysilane available fromDow Corning Corporation of Midland, Michigan. ³Triallylisocyanurateavailable from Nippon Kasei Chemical Company Limited ⁴Epoxy functionalsilane available from Silquest. ⁵γ-Aminopropyltriethoxysilane availablefrom Silquest. ⁶n-Butyl titanate available from DuPont ™. ⁷Availablefrom Sigma-Aldrich ⁸Isobutyltrimethoxysilane available from Dow CorningCorporation of Midland, Michigan. ⁹Vinyldimethylchlorosilane availablefrom Dow Corning Corporation of Midland, Michigan.¹⁰2,5-thiophenediylbis(5-tert-butyl-1,3-benzoxazole), commerciallyavailable from Ciba.

TABLE 5 Viscosity (1 s⁻¹) Days Aged Room Temperature % Change inViscosity 1 7 14 after 14 days Table 3 Adhesive 341.07 457.26 670.0396.45 with MCP Table 3 Adhesive 297.48 393.81 418.10 40.55 with MCP-1

As Table 5 confirms, the introduction of the isomer reducing agent tothe adhesive formulation resulted in a significant reduction in theviscosity increase of the adhesive after 14 days of aging.

Next, the adhesives were applied to Alclad™ aluminum substrates(available from Alcoa) and cured for 20 minutes at 85° C. and having 8mil bond line thickness. One half of the samples were evaluated at roomtemperature and aged, while the remaining samples were placed in apressure cooker tester (PCT) for 24 hours at 1 additional atmosphere andevaluated after aging. The lap shear adhesive properties of the coatedsubstrates appropriately aged were evaluated for peak stress, in poundsper square inch (PSI), with the results summarized in Table 6.

TABLE 6 Peak Stress (PSI) Dry Adhesion PCT Initial Week2 Week1 Week2Table 3 Adhesive 431.16 400.51 513.01 527.18 with MCP Table 3 Adhesive495.94 424.66 563.12 533.39 with MCP-1

As Table 6 confirms, the introduction of an isomer reducing agent to theadhesive composition resulted in comparable adhesion to Alclad™ aluminumsubstrates as compared with samples that did not include the isomerreducing agent.

D. Comparison of Physical Properties of Adhesive with MCP-1 VersusCommercially Available Adhesives on a Wide Variety of Substrates

Next, Adhesive MCP-1 was compared with various commercially availableadhesive compositions (DOW CORNING® 866, 3-6265, 3-6265 HP, and 7091),which are known to have excellent adhesion to a variety of both metaland plastic substrates. The incumbent one part silicone adhesive used inindustrial processes generally use one of two cure processes. A heatactivated Pt catalyzed addition chemistry that utilizes silicone hydridebased crosslinkers with silicone vinyl polymers is utilized by DOWCORNING® 866, 3-6265, and 3-6265 HP. DOW CORNING® 7091 utilizes acondensation cure in which alkoxy silicone polymers equivalent to thoseutilized in ARPB which are triggered by exposure to moisture in theatmosphere.

The addition cured systems cure rapidly but take elevated temperature todevelop adhesion (greater than 120° C. and typically 150° C.). These Ptbased systems are known to be inhibited by numerous plastic substratesespecially those containing basic substituent's like polyamides andepoxies. The elevated temperatures also lead to water physisorbed on thesurface of plastics and metals to devolatilize. The devolatilizationduring the curing process can lead to bubbling and voiding issues. Thisis believed to be a combination of liquid water devolatilization andinteraction of the water/SiH moieties in the presence of the platinumcatalyst. The condensation curable adhesive develops adhesion at roomtemperature to a wider variety of substrate but adhesion typically takesdays to weeks to fully develop.

Sample preparation on Alclad™ Panels:

1″×3″ Al Alclad™ Panels were cleaned with acetone (3 samples prepared).Bondlines were established using Spheriglass spacer beads (PottersIndustries Inc. 350 North Baker Drive, Canby, Oreg. 97013-0607)appropriate with the application (i.e., 8 mil (200 micron)). Larger bondlines used 20 mil wire.

A ⅜″ binder clip was used with both spacers methods to secure substratesduring cure. Cure at time and temperature were specified in resultsbelow. Testing was carried out on Instron 5566 tensiometer at 2 inchesper minute (Instron Worldwide Headquarters, 825 University Ave.,Norwood, Mass. 02062-2643). The results are summarized in Table 7 and 8below:

TABLE 7 DOW DOW DOW DOW Table 3 CORNING ® CORNING ® CORNING ® CORNING ®Adhesive with Product # 866 3-6265 3-6265HP 7091 MCP-1 Curing PtAddition Pt Addition Pt Addition Condensation Radical/ MechanismCondensation Durometer, 57 60 67 37 36 Shore A Tensile 925 700 815 400420 Strength, psi Elongation, % 210 165 145 590 285 Modulus, 440 425 56070 135 100%, psi Lap shear to 725 610 800 430 400 Alclad ™ Al, psiViscosity low 54,000 970,000 1,140,000 shear Viscosity high 49000230,000 300,000 shear Specific 1.3 1.34 1.33 1.42 1.09 Gravity Typicalcure, 30 min 20 min 20 min 3 days 20 min time at bond @150° C., @150°C., @150° C., @25° C. @85° C., line temp 60 min 45 min 45 min 1-2 min@125° C. @125° C. @125° C. @>100° C.

As Table 7 confirms, the adhesive composition (Table 3 Adhesive withMCP-1) according to the present invention exhibited adequate physicalproperties in terms of Durometer hardness, tensile strength, elongation,modulus and lap shear on Alclad™ Al substrates. In addition, theadhesive composition (Table 3 Adhesive with MCP-1) according to thepresent invention cured at lower temperatures (actual cure condition orbond line cure condition) than platinum catalyzed addition chemistryadhesive systems and in substantially shorter time periods thancondensation curable adhesive systems.

Sample Preparation on a Wide Variety of Metal and Plastic Substrates:

1″×3″ panels of the various substrates were cleaned with acetone (3samples prepared). Bondlines were established using Spheriglass spacerbeads (Potters Industries Inc. 350 North Baker Drive, Canby, Oreg.97013-0607) appropriate with the application (i.e., 8 mil (200 micron)).Larger bond lines used 20 mil wire.

A ⅜″ binder clip was used with both spacers methods to secure substratesduring cure. Cure at time and temperature were specified in resultsbelow. Testing was carried out on Instron 5566 tensiometer at 2 inchesper minute (Instron Worldwide Headquarters, 825 University Ave.,Norwood, Mass. 02062-2643).

TABLE 8 DOW DOW DOW Table 3 CORNING ® CORNING ® CORNING ® Adhesive with866 3-6265 3-6265 HP MCP-1 PSI % CF PSI % CF PSI % CF PSI % CF Alclad ™Al¹¹ 12 10% 20  100% 20  20% 40 100% (Peel) 3105 PBT¹² (lap 538 100 476100 617 100 300 100% shear) 3105 PBT (peel) 18 70 16 100 16 100 50 100%LCP¹³ (lap shear) 107 0 0  0 100  0 290 100% PA66¹⁴ (peel) 16 90 12 10010  50 34 100% PC¹⁵ (peel) 0 0 0  0 0  0 95 100% PE¹⁶ (peel) 0 0 0  0 0 0 12  50% FR-4¹⁷ (lap shear) 355 100 477 100 658 100 308 100% FR-4(peel) 12 100 20 100 22 100 44 100% ¹¹Alclad Aluminum, Type AD Q-Panel2024T3 from Q-Lab Corporation, 800., Cleveland, OH 44145 USA. ¹²3105PBT: Polybutylene terephthalate Celanex ® 3105 available from TiconaNorth America, Florence, KY 41042. ¹³LCP: liquid crystal polymer,Xydar ® available from Solvay Chemicals, Houston, Texas 77098 USA.¹⁴PA66: Polyamide Ultramid ® available at BASF Corporation, FlorhamPark, NJ 07932 USA. ¹⁵PC: Polycarbonate Lexan ® available from, SABICInnovative Plastics Pittsfield, MA 01201, USA. ¹⁶PE: Polyethylene MediumHigh Density PE (PEX), available at Lowes, Mooresville, NC 28117 USA¹⁷FR-4: Epoxy glass fiber laminates available from Norplex-Micarta,Postville, Iowa, USA.

As Table 8 illustrates, the adhesive composition (Table 3 Adhesive withMCP-1) according to the present invention exhibited adequate adhesionand cohesion to both aluminum and plastic substrates and was the onlyadhesive composition to adhere to polyethylene.

Table 9 below shows the impact on cure system of voiding caused bymoisture on surface of certain plastic substrates, here Ticona Celanex®3300D PBT and BASF polyamide PA66.

TABLE 9 Product # DOW DOW DOW Table 3 Water CORNING ® CORNING ®CORNING ® Adhesive Content 3-6265 3-6265 HP 7091 with MCP-1 Ticona 0.20%few bubbles no bubbling sig bubbling no bubbling Celanex ® 0.33% sigbubbling few bubbles sig bubbling no bubbling 3300D PBT BASF 1.50% sigbubbling some bubbles sig bubbling no bubbling polyamide 1.90% sigbubbling sig bubbling sig bubbling no bubbling PA66 2.65% sig bubblingsig bubbling sig bubbling sig bubbling

As Table 9 illustrates, the adhesive composition (Table 3 Adhesive withMCP-1) according to the present invention experienced no bubbling oneither substrate at any of the provided water content levels.

E. Evaluation of Clustered Functional Polyorganosiloxane withAlternative Radical Initiators

Using the process cited above but replacing RBM-9020 modifier adichlorobenzoylperoxide based initiator with Perkadox L-50-PS and highertemperature benzoyl peroxide based initiator (See Table 6), highertemperature curing materials were evaluated over four differentsubstrates (Polybutyl Terephthalate (PBT), Polyphenyl Sulphone (PPS),Alclad™ aluminum substrates (AL), and aluminum die cast metal (ADC))under different curing conditions.

TABLE 10 MCP-1 72.54 ARBP-1 19.55 Perkadox L-50S-PS¹¹ 1.88 OFS-6030Silane² 1.99 TAIC³ 0.49 TYZOR TNBT⁴ 0.62 A-1110⁵ 0.1 A186⁶ 0.62-Mercaptobenzothiazole⁷ 0.15 OFS-2306 Silane⁸ 1.96 OFS-1719 Silane⁹ 0.1TINOPAL OB¹⁰ 0.02 ¹¹Dibenzoyl peroxide available from Akzo-Nobel

TABLE 11A Cure Temp Time PBT PPS method (deg C.) (mins) N/cm² CF % N/cm²CF % Press 120 2 220 100 205 100 4 218 100 228 100 6 207 100 243 100Oven 120 4 129 100 148 100 10 175 100 171 100 100 20 173 100 201 100 30180 100 185 100 % CF = percentage cohesive failure

TABLE 11B Cure Temp Time AL ADC method (deg C.) (mins) N/cm² CF % N/cm²CF % Press 120 2 182 100 202 100 4 201 100 235 100 6 248 100 213 100Oven 120 4 242 100 205 100 10 260 100 225 100 100 20 216 100 252 100 30213 100 274 100 % CF = percentage cohesive failure

The results from Tables 11A and 11B confirm that adhesive compositionsformed with the clustered functional polyorganosiloxane of the presentinvention including the isomer reducing agent but utilizing analternative radical initiator exhibited good performance over a widevariety of metal and plastic substrates and under varying curingconditions.

F. Evaluation of Dispensing Properties for Thermal Radical Cure SiliconeAdhesive Compositions

Next, the dispensing properties for the thermal radical curable siliconecompositions were evaluated.

The materials provided in Table 12 were cold blended in a HauschildSpeedmixer DAC 150.1 FV-K available from FlackTek Inc, Landrum, S.C.29356 U.S.A.

TABLE 12 RBM-9020 MODIFIER¹ 32.22 OFS-6030 Silane² 21.99 TAIC³ 5.47TYZOR TNBT⁴ 6.92 A-1110⁵ 1.12 A186⁶ 6.70 2-Mercaptobenzothiazole⁷ 1.67OFS-2306 Silane⁸ 21.88 OFS-1719 Silane⁹ 1.12 TINOPAL OB¹⁰ 0.22

The components in Table 13 were also mixed in the speedmixer prior toevaluation for dispensability.

TABLE 13 MCP + MCP-112 + MCP + Components MCP MCP+ SFD-120 AP3¹² ARPB-1MCP-1 72 92  72 72 72 SFD-120 — — 20 — — AP3¹² — — — 20 — ARPB-1 — — — —20 Table 12 mixture  8 8  8  8  8 TOTAL 80 100  100  100  100  DispenseRating  1 1  1  1  4 (5 = best) ¹²AP3-DOW CORNING ® 3-1717 -Trimethoxysilylethyl)tetramethyldisiloxane-terminatedpolydimethylsiloxane (DOW CORNING ® SFD-117), about 2000 cps.

Dispense and stringing checks were done using an EFD 1000-XL syringedispenser (Available from Nordson EFD, East Providence, R.I. 02914U.S.A. Materials being compared were dispensed from 30 ml EFD syringesat 50 pounds per square inch of air pressure.

The rating is a subjective rating based on the ability to control theadhesive bead at an applied pressure. The rating is a reflection of thetendency and length of any bead on termination of applied pressure. Evenwith superior cure and adhesion to multiple substrates, the inability toroutinely dispense a bead or dot of adhesive on a substrate, in a timelymanner, can stop commercial adoption.

As Table 13 confirms, the ARPB-1 defined above improves dispensingwithout loss of mechanical properties. It also provides a secondary curemechanism by which any surface tack in the radical cured system due tooxygen inhibition can be overcome. It should also be noted that thealkoxy functionality is highly desirable for adhesion to mineral andmetallic surfaces.

The instant disclosure has been described in an illustrative manner, andit is to be understood that the terminology which has been used isintended to be in the nature of words of description rather than oflimitation. Many modifications and variations of the instant disclosureare possible in light of the above teachings. It is, therefore, to beunderstood that within the scope of the appended claims, the instantdisclosure may be practiced otherwise than as specifically described.

The invention claimed is:
 1. A stable thermal radical curable siliconeadhesive composition comprising: (I) a clustered functionalpolyorganosiloxane having at least one radical curable group selectedfrom an acrylate group and a methacrylate group; (II) a reactive resinand polymer comprising: (a) an organopolysiloxane polymer of the formula(R⁷O)_(3-z)R⁶ _(z)Si-Q-(R²⁵ ₂SiO_(2/2))_(y)-Q-SiR⁶ _(z)(OR⁷)_(3-z),wherein each R²⁵ is independently a monovalent hydrocarbon radicalhaving 1 to 6 carbon atoms, each R⁶ independently is a monovalenthydrocarbon radical having 1 to 6 carbon atoms, each R⁷ independently isselected from the group consisting of an alkyl radical and alkoxyalkylradical, Q is a divalent linking radical, the subscript z has a value of0, 1 or 2, and the subscript y has a value of 60 to 1000; and (b) analkoxy-functional organopolysiloxane resin comprising the reactionproduct of a reaction of: (i) an alkenyl-functional siloxane resincomprising R²⁶ ₃SiO_(1/2) units and SiO_(4/2) units, wherein each R²⁶ isindependently a monovalent hydrocarbon radical having 1 to 6 carbonatoms with the proviso that at least one R²⁶ is an alkenyl radical,wherein the molar ratio of the R²⁶ ₃SiO_(1/2) units to SiO_(4/2) unitshas a value of from 0.5/1 to 1.5/1; (ii) an alkoxysilane-functionalorganosiloxane compound having at least one silicon-bonded hydrogen atomat a molecular terminal; and (iii) an endcapper of the formula R¹⁷₃SiO—(R¹⁷ ₂SiO)_(s)—SiR¹⁷ ₂H or R¹⁸ ₃SiO—(R¹⁸ ₂SiO)_(t)—(HR¹⁸SiO)—SiR¹⁸₃ or combinations thereof, wherein each R¹⁷ and R¹⁸ are independently amonovalent hydrocarbon group and wherein subscripts s and tindependently have a value ranging from 0 to 10; in the presence of (iv)a hydrosilylation catalyst; (III) a radical initiator; (IV) a moisturecure initiator; and (V) a crosslinker.
 2. The adhesive compositionaccording to claim 1, wherein the clustered functionalpolyorganosiloxane (I) comprises the reaction product of: a) apolyorganosiloxane having an average, per molecule, of at least 2aliphatically unsaturated organic groups, b) apolyorganohydrogensiloxane having an average, per molecule, of 4 to 15silicon atoms and at least 4 silicon bonded hydrogen atoms peraliphatically unsaturated organic group in component a), and c) areactive species having, per molecule, at least one aliphaticallyunsaturated organic group and one or more curable groups selected fromacrylate groups and methacrylate groups, in the presence of d) ahydrosilylation catalyst and e) an isomer reducing agent.
 3. Theadhesive composition according to claim 1, wherein the clusteredfunctional polyorganosiloxane (I) comprises a reaction product of areaction of: a) a polyorganosiloxane having an average, per molecule, ofat least 2 aliphatically unsaturated organic groups, b) apolyorganohydrogensiloxane having an average, per molecule, of 4 to 15silicon atoms and at least 4 silicon bonded hydrogen atoms peraliphatically unsaturated organic group in component a), and c) areactive species having, per molecule, at least one aliphaticallyunsaturated organic group and one or more curable groups selected fromacrylate groups and methacrylate groups, in the presence of d) ahydrosilylation catalyst.
 4. The adhesive composition according to claim2, wherein a weight percent of silicon bonded hydrogen atoms in thepolyorganohydrogensiloxane b) divided by a weight percent ofaliphatically unsaturated organic groups in the polyorganosiloxane a)(the SiH_(b)/Vi_(a) ratio) ranges from 4/1 to 20/1 and the clusteredfunctional polyorganosiloxane (I) prepared by the process has more thanone curable group at each molecular terminal of the polyorganosiloxaneof component a).
 5. The adhesive composition according to claim 1,wherein a weight ratio of the organopolysiloxane polymer (a) to thealkoxy-functional organopolysiloxane resin (b) varies from 75/25 to35/65.
 6. The adhesive composition according to claim 1, wherein Q is adivalent linking radical selected from a divalent hydrocarbon radical, adivalent siloxane radical, and combinations thereof, wherein the numberof carbon atoms in the hydrocarbon radical ranges from 2 to 12 andwherein the number of siloxane repeat units in the siloxane radicalranges from 0 to
 20. 7. The adhesive composition according to claim 1,wherein the endcapper (iii) comprises Me₃Si—O—Si(Me)H—OSiMe₃ orMe₃Si—O—Si(Me)₂—OSiHMe₂, wherein Me denotes methyl.
 8. The adhesivecomposition according to claim 1, wherein the alkoxysilane-functionalorganosiloxane compound (ii) is of the formulaHSi(R²⁷)₂OSi(R²⁷)₂CH₂CH₂SiR²⁷ _(zz)(OR²⁷)_(3-zz) wherein each R²⁷ isindependently a monovalent hydrocarbon having 1 to 6 carbon atoms andwherein the subscript zz is 0 or
 1. 9. The adhesive compositionaccording to claim 1, wherein the reactive resin and polymer (II)comprises from 5 to 50 weight percent of the total weight of theadhesive composition.
 10. The adhesive composition according to claim 1,wherein alkenyl-functional siloxane resin (i) includes from 0.5 to 4weight percent alkenyl functionality, based on the total weight of thealkenyl-functional siloxane resin (i).
 11. The adhesive compositionaccording to claim 1, wherein the radical initiator (III) comprises from0.01 to 15 weight percent of the total weight of the adhesivecomposition.
 12. The adhesive composition according to claim 1, whereinthe moisture cure catalyst (IV) comprises from 0.001 to 5 weight percentof the total weight of the reactive resin and polymer (II).
 13. Theadhesive composition according to claim 1, wherein the crosslinker (V)is a condensation reaction crosslinker selected from the groupconsisting of trialkoxysilanes, acetoxysilanes, ketoximinosilanes, alkylorthosilicates, methylvinyl bis(n-methylacetamido) silane, andcombinations thereof.
 14. The adhesive composition according to claim 1further comprising an iron oxide pigment.
 15. A method for forming acured silicone adhesive composition on a substrate, the methodcomprising: (a) forming a stable thermal radical curable siliconeadhesive composition comprising: (I) a clustered functionalpolyorganosiloxane having at least one radical curable group selectedfrom an acrylate group and a methacrylate group; (II) a reactive resinand polymer comprising: (a) an organopolysiloxane polymer of the formula(OR⁷)_(3-z)R⁶ _(z)Si-Q-(R²⁵ ₂SiO_(2/2))_(y)-Q-SiR⁶ _(z)(OR⁷)_(3-z),wherein each R²⁵ is independently a monovalent hydrocarbon radicalhaving 1 to 6 carbon atoms, each R⁶ independently is a monovalenthydrocarbon radical having 1 to 6 carbon atoms, each R⁷ independently isselected from the group consisting of an alkyl radical and alkoxyalkylradical, Q is a divalent linking radical, the subscript z has a value of0, 1 or 2, and the subscript y has a value of 60 to 1000, and (b) analkoxy-functional organopolysiloxane resin comprising the reactionproduct of a reaction of: (i) an alkenyl-functional siloxane resincomprising R²⁶ ₃SiO_(1/2) units and SiO_(4/2) units, wherein each R²⁶ isindependently a monovalent hydrocarbon radical having 1 to 6 carbonatoms with the proviso that at least one R²⁶ is an alkenyl radical,wherein the molar ratio of the R²⁶ ₃SiO_(1/2) units to SiO_(4/2) unitshas a value of from 0.5/1 to 1.5/1; (ii) an alkoxysilane-functionalorganosiloxane compound having at least one silicon-bonded hydrogen atomat a molecular terminal; and (iii) an endcapper of the formula R¹⁷₃SiO—(R¹⁷ ₂SiO)_(s)—SiR¹⁷ ₂H or R¹⁸ ₃SiO—(R¹⁸ ₂SiO)_(t)—(HR¹⁸SiO)—SiR¹⁸₃ or combinations thereof, wherein each R¹⁷ and R¹⁸ are independently amonovalent hydrocarbon group and wherein subscripts s and t have a valueranging from 0 to 10; in the presence of a (iv) hydrosilylationcatalyst; (III) a radical initiator; (IV) a moisture cure initiator; and(V) a crosslinker; (b) applying the stable thermal radical curablesilicone adhesive composition to the substrate; and (c) curing theapplied stable thermal radical curable silicone adhesive composition toform the cured silicone adhesive composition on the substrate.
 16. Themethod according to claim 15, wherein the clustered functionalpolyorganosiloxane having at least one radical curable group selectedfrom an acrylate group and a methacrylate group (I) comprises a reactionproduct of a reaction of: a) a polyorganosiloxane having an average, permolecule, of at least 2 aliphatically unsaturated organic groups, b) apolyorganohydrogensiloxane having an average, per molecule, of 4 to 15silicon atoms and at least 4 silicon bonded hydrogen atoms peraliphatically unsaturated organic group in component a), and c) areactive species having, per molecule at least one aliphaticallyunsaturated organic group and one or more curable groups selected fromacrylate groups and methacrylate groups, in the presence of d) ahydrosilylation catalyst and e) an isomer reducing agent.
 17. The methodaccording to claim 15, wherein the clustered functionalpolyorganosiloxane having at least one radical curable group selectedfrom an acrylate group and a methacrylate group (I) comprises a reactionproduct of a reaction of: a) a polyorganosiloxane having an average, permolecule, of at least 2 aliphatically unsaturated organic groups, b) apolyorganohydrogensiloxane having an average, per molecule, of 4 to 15silicon atoms and at least 4 silicon bonded hydrogen atoms peraliphatically unsaturated organic group in component a), and c) areactive species having, per molecule at least one aliphaticallyunsaturated organic group and one or more curable groups selected fromacrylate groups and methacrylate groups, in the presence of d) ahydrosilylation catalyst.
 18. The method according to claim 15, wherein(c) curing the applied stable thermal radical curable silicone adhesivecomposition on the substrate comprises thermally curing the appliedstable thermal radical curable silicone adhesive composition on thesubstrate.
 19. A cured silicone adhesive composition on a substrateformed in accordance with the method of claim
 15. 20. The adhesivecomposition according to claim 3, wherein a weight percent of siliconbonded hydrogen atoms in the polyorganohydrogensiloxane b) divided by aweight percent of aliphatically unsaturated organic groups in thepolyorganosiloxane a) (the SiH_(b)/Vi_(a) ratio) ranges from 4/1 to 20/1and the clustered functional polyorganosiloxane (I) prepared by theprocess has more than one curable group at each molecular terminal ofthe polyorganosiloxane of component a).